diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index c00b0247bb..e95a5a77ec 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -1470,12 +1470,51 @@ fn airBoolToInt(f: *Function, inst: Air.Inst.Index) !CValue {
     return local;
 }
 
+fn airStoreUndefined(f: *Function, dest_ptr: CValue) !CValue {
+    const is_debug_build = f.object.dg.module.optimizeMode() == .Debug;
+    if (!is_debug_build)
+        return CValue.none;
+
+    const writer = f.object.writer();
+    switch (dest_ptr) {
+        .local_ref => |i| {
+            const dest: CValue = .{ .local = i };
+            try writer.writeAll("memset(&");
+            try f.writeCValue(writer, dest);
+            try writer.writeAll(", 0xaa, sizeof(");
+            try f.writeCValue(writer, dest);
+            try writer.writeAll("));\n");
+        },
+        .decl_ref => |decl| {
+            const dest: CValue = .{ .decl = decl };
+            try writer.writeAll("memset(&");
+            try f.writeCValue(writer, dest);
+            try writer.writeAll(", 0xaa, sizeof(");
+            try f.writeCValue(writer, dest);
+            try writer.writeAll("));\n");
+        },
+        else => {
+            try writer.writeAll("memset(");
+            try f.writeCValue(writer, dest_ptr);
+            try writer.writeAll(", 0xaa, sizeof(*");
+            try f.writeCValue(writer, dest_ptr);
+            try writer.writeAll("));\n");
+        },
+    }
+    return CValue.none;
+}
+
 fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
     // *a = b;
     const bin_op = f.air.instructions.items(.data)[inst].bin_op;
     const dest_ptr = try f.resolveInst(bin_op.lhs);
     const src_val = try f.resolveInst(bin_op.rhs);
 
+    const src_val_is_undefined =
+        if (f.air.value(bin_op.rhs)) |v| v.isUndef() else false;
+    if (src_val_is_undefined)
+        return try airStoreUndefined(f, dest_ptr);
+
     const writer = f.object.writer();
     switch (dest_ptr) {
         .local_ref => |i| {
diff --git a/test/behavior.zig b/test/behavior.zig
index 9ef98bd772..4f78a9d35a 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -5,12 +5,15 @@ test {
     _ = @import("behavior/basic.zig");
     _ = @import("behavior/bitcast.zig");
     _ = @import("behavior/bool.zig");
+    _ = @import("behavior/bugs/624.zig");
     _ = @import("behavior/bugs/655.zig");
     _ = @import("behavior/bugs/679.zig");
     _ = @import("behavior/bugs/704.zig");
     _ = @import("behavior/bugs/1486.zig");
     _ = @import("behavior/bugs/2346.zig");
+    _ = @import("behavior/bugs/2692.zig");
     _ = @import("behavior/bugs/2889.zig");
+    _ = @import("behavior/bugs/3586.zig");
     _ = @import("behavior/bugs/4560.zig");
     _ = @import("behavior/bugs/4769_a.zig");
     _ = @import("behavior/bugs/4769_b.zig");
@@ -30,6 +33,9 @@ test {
     _ = @import("behavior/underscore.zig");
     _ = @import("behavior/usingnamespace.zig");
     _ = @import("behavior/while.zig");
+    _ = @import("behavior/this.zig");
+    _ = @import("behavior/member_func.zig");
+    _ = @import("behavior/translate_c_macros.zig");
 
     if (builtin.object_format != .c) {
         // Tests that pass for stage1 and stage2 but not the C backend.
@@ -38,14 +44,11 @@ test {
         _ = @import("behavior/atomics.zig");
         _ = @import("behavior/basic_llvm.zig");
         _ = @import("behavior/bugs/394.zig");
-        _ = @import("behavior/bugs/624.zig");
         _ = @import("behavior/bugs/1277.zig");
         _ = @import("behavior/bugs/1500.zig");
         _ = @import("behavior/bugs/1741.zig");
         _ = @import("behavior/bugs/2006.zig");
-        _ = @import("behavior/bugs/2692.zig");
         _ = @import("behavior/bugs/3112.zig");
-        _ = @import("behavior/bugs/3586.zig");
         _ = @import("behavior/cast.zig");
         _ = @import("behavior/error.zig");
         _ = @import("behavior/eval.zig");
@@ -55,7 +58,6 @@ test {
         _ = @import("behavior/generics.zig");
         _ = @import("behavior/math.zig");
         _ = @import("behavior/maximum_minimum.zig");
-        _ = @import("behavior/member_func.zig");
         _ = @import("behavior/null_llvm.zig");
         _ = @import("behavior/optional.zig");
         _ = @import("behavior/pointers.zig");
@@ -65,8 +67,6 @@ test {
         _ = @import("behavior/slice.zig");
         _ = @import("behavior/struct_llvm.zig");
         _ = @import("behavior/switch.zig");
-        _ = @import("behavior/this.zig");
-        _ = @import("behavior/translate_c_macros.zig");
         _ = @import("behavior/union.zig");
         _ = @import("behavior/widening.zig");