diff --git a/cmd/w6c/cgen.c b/cmd/w6c/cgen.c
index b9be8429..db22bb22 100644
--- a/cmd/w6c/cgen.c
+++ b/cmd/w6c/cgen.c
@@ -4925,6 +4925,12 @@ cgexpr(Cg *c, Node *n, Local *locals)
 					ins1(c, A_PUSHQ, areg(D_AX));
 					ins2(c, A_MOVQ, amem(D_BX, 0), areg(D_AX));
 					ins1(c, A_PUSHQ, areg(D_AX));
+				} else if (off == 0 && def_isanydef(n->rhs->str)) {
+					/* A str `def` has no name(SB) header: cgexpr
+					 * materialises its literal as AX=ptr, BX=len. */
+					cgexpr(c, n->rhs, locals);
+					ins1(c, A_PUSHQ, areg(D_BX));
+					ins1(c, A_PUSHQ, areg(D_AX));
 				} else {
 					ins2(c, A_MOVQ, amem(D_BP, off + 8), areg(D_AX));
 					ins1(c, A_PUSHQ, areg(D_AX));
@@ -4948,6 +4954,10 @@ cgexpr(Cg *c, Node *n, Local *locals)
 					ins1(c, A_PUSHQ, areg(D_AX));
 					ins2(c, A_MOVQ, amem(D_BX, 0), areg(D_AX));
 					ins1(c, A_PUSHQ, areg(D_AX));
+				} else if (off == 0 && def_isanydef(n->lhs->str)) {
+					cgexpr(c, n->lhs, locals);
+					ins1(c, A_PUSHQ, areg(D_BX));
+					ins1(c, A_PUSHQ, areg(D_AX));
 				} else {
 					ins2(c, A_MOVQ, amem(D_BP, off + 8), areg(D_AX));
 					ins1(c, A_PUSHQ, areg(D_AX));
diff --git a/selfhost/cmd/wcc/cgenexpr.ww b/selfhost/cmd/wcc/cgenexpr.ww
index fc4c6a7f..a6b48325 100644
--- a/selfhost/cmd/wcc/cgenexpr.ww
+++ b/selfhost/cmd/wcc/cgenexpr.ww
@@ -5808,6 +5808,14 @@ fn cgstreqpush(c: *cgen, op: *syntax.node) void = {
 			emitline("\tPUSHQ\tAX\n");
 			return;
 		};
+		if (lc == nil && deflookup(c, nm)) {
+			// A str def has no name(SB) header. Its ordinary expression
+			// load materialises the literal as AX=ptr, BX=len.
+			cgexpr(c, op);
+			emitline("\tPUSHQ\tBX\n");
+			emitline("\tPUSHQ\tAX\n");
+			return;
+		};
 		let off: i32 = 0;
 		if (lc != nil) { off = lc.off; };
 		emitline("\tMOVQ\t");
diff --git a/test/lang/str_def_equality_test.ww b/test/lang/str_def_equality_test.ww
new file mode 100644
index 00000000..57141a51
--- /dev/null
+++ b/test/lang/str_def_equality_test.ww
@@ -0,0 +1,20 @@
+// String equality must materialise a module def literal instead of treating
+// its name as a frame-local string header. Use a duplicated local so pointer
+// equality cannot accidentally satisfy the content comparison.
+
+package str_def_equality_test;
+
+import strings;
+
+def expected: str = "dynamic string versus def";
+
+@test fn dynamic_string_and_def_compare_by_content() void = {
+	let observed: str = strings.dup(expected);
+	assert(observed == expected);
+	assert(expected == observed);
+	assert(!(observed != expected));
+	assert(!(expected != observed));
+	let different: str = strings.concat(observed, "!");
+	assert(different != expected);
+	assert(expected != different);
+};