diff --git a/dlls/jscript/engine.c b/dlls/jscript/engine.c
index 6d336fe5a01..3d21b212595 100644
--- a/dlls/jscript/engine.c
+++ b/dlls/jscript/engine.c
@@ -1683,10 +1683,27 @@ HRESULT less_expression_eval(exec_ctx_t *ctx, expression_t *_expr, DWORD flags,
     return return_bool(ret, b);
 }
 
-HRESULT lesseq_expression_eval(exec_ctx_t *ctx, expression_t *expr, DWORD flags, jsexcept_t *ei, exprval_t *ret)
+/* ECMA-262 3rd Edition    11.8.3 */
+HRESULT lesseq_expression_eval(exec_ctx_t *ctx, expression_t *_expr, DWORD flags, jsexcept_t *ei, exprval_t *ret)
 {
-    FIXME("\n");
-    return E_NOTIMPL;
+    binary_expression_t *expr = (binary_expression_t*)_expr;
+    VARIANT rval, lval;
+    BOOL b;
+    HRESULT hres;
+
+    TRACE("\n");
+
+    hres = get_binary_expr_values(ctx, expr, ei, &lval, &rval);
+    if(FAILED(hres))
+        return hres;
+
+    hres = less_eval(ctx, &rval, &lval, ei, &b);
+    VariantClear(&lval);
+    VariantClear(&rval);
+    if(FAILED(hres))
+        return hres;
+
+    return return_bool(ret, !b);
 }
 
 HRESULT greater_expression_eval(exec_ctx_t *ctx, expression_t *expr, DWORD flags, jsexcept_t *ei, exprval_t *ret)
diff --git a/dlls/jscript/tests/lang.js b/dlls/jscript/tests/lang.js
index f94284f28e4..2799b1568be 100644
--- a/dlls/jscript/tests/lang.js
+++ b/dlls/jscript/tests/lang.js
@@ -202,4 +202,11 @@ ok("abcd" < "abce", "abce < abce failed");
 ok("" < "x", "\"\" < \"x\" failed");
 ok(!(0 < 0), "0 < 0");
 
+ok(1 <= 3.4, "1 <= 3.4 failed");
+ok(!(3.4 <= 1), "3.4 <= 1");
+ok("abc" <= "abcd", "abc <= abcd failed");
+ok("abcd" <= "abce", "abce <= abce failed");
+ok("" <= "x", "\"\" <= \"x\" failed");
+ok(0 <= 0, "0 <= 0 failed");
+
 reportSuccess();