diff --git a/analyser/module_analyser_stmt.c2 b/analyser/module_analyser_stmt.c2
index be4b2f453..70f63b816 100644
--- a/analyser/module_analyser_stmt.c2
+++ b/analyser/module_analyser_stmt.c2
@@ -437,6 +437,11 @@ fn void Analyser.analyseAssertStmt(Analyser* ma, Stmt* s) {
 
     Expr* inner = a.getInner();
     ma.checker.check(builtins[BuiltinKind.Bool], qt, a.getInner2(), inner.getLoc());
+
+    if (a.getCall()) {
+        qt = ma.analyseExpr(a.getCall2(), true, RHS);
+        if (qt.isInvalid()) return;
+    }
 }
 
 fn void Analyser.analyseReturnStmt(Analyser* ma, Stmt* s) {
diff --git a/ast/assert_stmt.c2 b/ast/assert_stmt.c2
index 9125ab6b7..6f84bf6b7 100644
--- a/ast/assert_stmt.c2
+++ b/ast/assert_stmt.c2
@@ -22,15 +22,18 @@ import string_buffer;
 public type AssertStmt struct @(opaque) {
     Stmt base;
     Expr* inner;
+    Expr* call;
 }
 
 public fn AssertStmt* AssertStmt.create(ast_context.Context* c,
-                                          SrcLoc loc,
-                                          Expr* inner)
+                                        SrcLoc loc,
+                                        Expr* inner,
+                                        Expr* call)
 {
     AssertStmt* s = c.alloc(sizeof(AssertStmt));
     s.base.init(StmtKind.Assert, loc);
     s.inner = inner;
+    s.call = call;
 #if AstStatistics
     Stats.addStmt(StmtKind.Assert, sizeof(AssertStmt));
 #endif
@@ -38,16 +41,22 @@ public fn AssertStmt* AssertStmt.create(ast_context.Context* c,
 }
 
 fn Stmt* AssertStmt.instantiate(AssertStmt* s, Instantiator* inst) {
-    return (Stmt*)AssertStmt.create(inst.c, s.base.loc, s.inner.instantiate(inst));
+    return (Stmt*)AssertStmt.create(inst.c, s.base.loc, s.inner.instantiate(inst),
+                                    s.call ? s.call.instantiate(inst) : nil);
 }
 
 public fn Expr* AssertStmt.getInner(const AssertStmt* s) { return s.inner; }
 
 public fn Expr** AssertStmt.getInner2(AssertStmt* s) { return &s.inner; }
 
+public fn Expr* AssertStmt.getCall(const AssertStmt* s) { return s.call; }
+
+public fn Expr** AssertStmt.getCall2(AssertStmt* s) { return &s.call; }
+
 fn void AssertStmt.print(const AssertStmt* s, string_buffer.Buf* out, u32 indent) {
     s.base.printKind(out, indent);
     out.newline();
     s.inner.print(out, indent + 1);
+    if (s.call) s.call.print(out, indent + 1);
 }
 
diff --git a/ast/utils.c2 b/ast/utils.c2
index 3d8b45a08..91275b536 100644
--- a/ast/utils.c2
+++ b/ast/utils.c2
@@ -41,7 +41,7 @@ static_assert(80, sizeof(FunctionDecl));
 static_assert(8, sizeof(Stmt));
 static_assert(12, sizeof(GotoStmt));
 static_assert(24, sizeof(LabelStmt));
-static_assert(16, sizeof(AssertStmt));
+static_assert(24, sizeof(AssertStmt));
 static_assert(8, sizeof(DeclStmt));
 static_assert(16, sizeof(SwitchStmt));
 static_assert(24, sizeof(AsmStmt));
diff --git a/common/ast_builder.c2 b/common/ast_builder.c2
index be5d97bbb..c814b8a4a 100644
--- a/common/ast_builder.c2
+++ b/common/ast_builder.c2
@@ -883,8 +883,8 @@ public fn SwitchCase* Builder.actOnCase(Builder* b,
                              conds, num_conds, stmts, num_stmts);
 }
 
-public fn Stmt* Builder.actOnAssertStmt(Builder* b, SrcLoc loc, Expr* inner) {
-    return (Stmt*)AssertStmt.create(b.context, loc, inner);
+public fn Stmt* Builder.actOnAssertStmt(Builder* b, SrcLoc loc, Expr* inner, Expr* call) {
+    return (Stmt*)AssertStmt.create(b.context, loc, inner, call);
 }
 
 public fn Stmt* Builder.actOnBreakStmt(Builder* b, SrcLoc loc) {
diff --git a/compiler/compiler.c2 b/compiler/compiler.c2
index 773916220..e019795a7 100644
--- a/compiler/compiler.c2
+++ b/compiler/compiler.c2
@@ -270,7 +270,8 @@ fn void Compiler.build(Compiler* c,
                                 c.astPool,
                                 c.builder,
                                 &c.kwinfo,
-                                target.getFeatures());
+                                target.getFeatures(),
+                                c.target.hasAsserts());
 
     ast.initialize(c.context, c.astPool, c.targetInfo.intWidth / 8, color.useColor());
 
diff --git a/generator/ast_visitor.c2 b/generator/ast_visitor.c2
index 3f20a181e..26ebc1deb 100644
--- a/generator/ast_visitor.c2
+++ b/generator/ast_visitor.c2
@@ -218,6 +218,8 @@ fn void Visitor.handleStmt(Visitor* v, Stmt* s) {
     case Assert:
         AssertStmt* a = (AssertStmt*)s;
         v.handleExpr(a.getInner());
+        Expr* call = a.getCall();
+        if (call) v.handleExpr(call);
         break;
     }
 }
diff --git a/generator/c/c_generator.c2 b/generator/c/c_generator.c2
index 56d5fd869..0dd8005d0 100644
--- a/generator/c/c_generator.c2
+++ b/generator/c/c_generator.c2
@@ -1431,17 +1431,6 @@ const char[] C_defines =
     #define ARRAY_SIZE(x) (sizeof(x)/sizeof((x)[0]))
     ```;
 
-const char[] C2_assert =
-    ```c
-    int dprintf(int fd, const char *format, ...);
-    void abort(void);
-    static int c2_assert(const char* filename, int line, const char* funcname, const char* condstr) {
-        dprintf(2, "%s:%d: function %s: Assertion failed: %s\n", filename, line, funcname, condstr);
-        abort();
-        return 0;
-    }
-    ```;
-
 const char[] C2_strswitch =
     ```c
     static int c2_strswitch(const char* s1, const char* s2) {
@@ -1508,10 +1497,6 @@ fn void Generator.emit_external_header(Generator* gen, bool enable_asserts, cons
 #endif
     out.add("#define to_container(type, member, ptr) ((type*)((char*)(ptr) - offsetof(type, member)))\n\n");
 
-    if (enable_asserts) {
-        out.add(C2_assert);
-    }
-
     // for switch(str):
     // String format: strings are prefixed by a length byte and concatenated as a single character array.
     // This minimizes memory use, cache misses and avoids extra symbols.
diff --git a/generator/c/c_generator_stmt.c2 b/generator/c/c_generator_stmt.c2
index f23f01fb7..ed541dba8 100644
--- a/generator/c/c_generator_stmt.c2
+++ b/generator/c/c_generator_stmt.c2
@@ -16,7 +16,6 @@
 module c_generator;
 
 import ast local;
-import source_mgr;
 import string_buffer;
 
 fn void Generator.emitVarDecl(Generator* gen, VarDecl* vd, string_buffer.Buf* out, bool emit_init, bool first) {
@@ -240,19 +239,12 @@ fn void Generator.emitStmt(Generator* gen, Stmt* s, u32 indent, bool newline) {
         if (!gen.enable_asserts) out.print(";//assert");
         AssertStmt* a = (AssertStmt*)s;
         out.add1('(');
-        Expr* inner = a.getInner();
-        gen.emitExpr(out, inner);
+        gen.emitExpr(out, a.getInner());
         out.add1(')');
-        if (gen.enable_asserts) {
-            source_mgr.Location loc = gen.sm.locate(s.getLoc());
-            const char* funcname = gen.cur_function.asDecl().getFullName();
-            out.print(" || c2_assert(\"%s\", %d, \"%s\", \"", loc.filename, loc.line, funcname);
-            // encode expression as a string
-            string_buffer.Buf* str = string_buffer.create(128, false, 0);
-            inner.printLiteral(str);
-            out.encodeBytes(str.data(), str.size(), '"');
-            str.free();
-            out.add("\")");
+        Expr* call = a.getCall();
+        if (call) {
+            out.add(" || ");
+            gen.emitExpr(out, call);
         }
         out.add(";\n");
         break;
diff --git a/libs/libc/c2_assert.c2i b/libs/libc/c2_assert.c2i
new file mode 100644
index 000000000..b98de7df4
--- /dev/null
+++ b/libs/libc/c2_assert.c2i
@@ -0,0 +1,14 @@
+module c2_assert;
+
+import stdio local;
+import stdlib local;
+
+public fn i32 c2_assert_fail(const char* filename @(auto_file),
+                             u32 line @(auto_line),
+                             const char* funcname @(auto_func),
+                             const char* condstr)
+{
+    dprintf(2, "%s:%d: function %s: Assertion failed: %s\n", filename, line, funcname, condstr);
+    abort();
+    return 0;
+}
diff --git a/libs/libc/manifest.yaml b/libs/libc/manifest.yaml
index 00369c6cd..3fe2adbd8 100644
--- a/libs/libc/manifest.yaml
+++ b/libs/libc/manifest.yaml
@@ -40,4 +40,4 @@ modules:
     - sys_utsname
     - uio
     - unistd
-
+    - c2_assert
diff --git a/parser/c2_parser.c2 b/parser/c2_parser.c2
index b173d3fe8..8d7ef939c 100644
--- a/parser/c2_parser.c2
+++ b/parser/c2_parser.c2
@@ -61,9 +61,12 @@ public type Parser struct @(opaque) {
     const string_list.List* features;
     const keywords.Info* kwinfo;
     bool is_interface;
+    bool has_asserts;
     u32 va_list_idx;
     u32 varargs_idx;
     u32 stdarg_idx;
+    u32 c2_assert_idx;
+    u32 c2_assert_fail_idx;
 
     stmt_list.List* stmt_lists;
     u32 stmt_list_count;
@@ -77,7 +80,8 @@ public fn Parser* create(SourceMgr* sm,
                            string_pool.Pool* pool,
                            ast_builder.Builder* builder,
                            const keywords.Info* kwinfo,
-                           const string_list.List* features)
+                           const string_list.List* features,
+                           bool has_asserts)
 {
     Parser* p = calloc(1, sizeof(Parser));
     p.sm = sm;
@@ -86,9 +90,12 @@ public fn Parser* create(SourceMgr* sm,
     p.builder = builder;
     p.features = features;
     p.kwinfo = kwinfo;
+    p.has_asserts = has_asserts;
     p.va_list_idx = pool.addStr("va_list", true);
     p.varargs_idx = pool.addStr("varargs", true);
     p.stdarg_idx = pool.addStr("stdarg", true);
+    p.c2_assert_idx = p.pool.addStr("c2_assert", true);
+    p.c2_assert_fail_idx = p.pool.addStr("c2_assert_fail", true);
 
     // create a stack of stmt_lists to re-use (resize stack if needed)
     p.stmt_lists = malloc(NumStmtLists * sizeof(stmt_list.List));
diff --git a/parser/c2_parser_stmt.c2 b/parser/c2_parser_stmt.c2
index 5816d907a..5f9512836 100644
--- a/parser/c2_parser_stmt.c2
+++ b/parser/c2_parser_stmt.c2
@@ -21,6 +21,7 @@ import constants local;
 import token local;
 import src_loc local;
 import string_list;
+import string_buffer;
 
 fn Stmt* Parser.parseStmt(Parser* p) {
     // TODO use Jump Table (combined one for multiple purposes?)
@@ -387,10 +388,36 @@ fn Stmt* Parser.parseAssertStmt(Parser* p) {
     SrcLoc loc = p.tok.loc;
     p.consumeToken();
     p.expectAndConsume(Kind.LParen);
+    SrcLoc eloc = p.tok.loc;
     Expr* inner = p.parseExpr();
+    u32 elen = p.prev_loc - eloc;
     p.expectAndConsume(Kind.RParen);
+    u32 loc_end = p.prev_loc;
     p.expectAndConsume(Kind.Semicolon);
-    return p.builder.actOnAssertStmt(loc, inner);
+
+    Expr* call = nil;
+    if (p.has_asserts) {
+        // add c2_assert.fail func designator
+        Ref[2] ref;
+        ref[0].loc = loc;
+        ref[0].name_idx = p.c2_assert_idx;
+        ref[1].loc = loc;
+        ref[1].name_idx = p.c2_assert_fail_idx;
+        p.addImplicitImport(p.c2_assert_idx, false);
+        Expr* func = p.builder.actOnMemberExpr(nil, ref, 2);
+
+        // encode expression as a string
+        string_buffer.Buf* buf = p.tokenizer.buf;
+        buf.clear();
+        inner.printLiteral(buf);
+        u32 msg_len = buf.size();
+        u32 msg_idx = p.pool.add(buf.data(), msg_len, true);
+        Expr* arg = p.builder.actOnStringLiteral(eloc, elen, msg_idx, msg_len);
+
+        // create call expression `assert.fail("expression")
+        call = p.builder.actOnCallExpr(loc, loc_end, func, &arg, 1);
+    }
+    return p.builder.actOnAssertStmt(loc, inner, call);
 }
 
 fn Stmt* Parser.parseBreakStmt(Parser* p) {
diff --git a/test/c_generator/stmts/assert.c2t b/test/c_generator/stmts/assert.c2t
index b5c284aef..f244bc536 100644
--- a/test/c_generator/stmts/assert.c2t
+++ b/test/c_generator/stmts/assert.c2t
@@ -19,8 +19,8 @@ int32_t main(void);
 
 int32_t main(void)
 {
-   (test_a) || c2_assert("file1.c2", 7, "test.main", "a");
-   (test_p) || c2_assert("file1.c2", 8, "test.main", "p");
+   (test_a) || c2_assert_fail("file1.c2", 7, "test.main", "a");
+   (test_p) || c2_assert_fail("file1.c2", 8, "test.main", "p");
    return 0;
 }