diff --git a/dlls/ntdll/signal_x86_64.c b/dlls/ntdll/signal_x86_64.c
index c6e9a9b4a29..7007db0a00e 100644
--- a/dlls/ntdll/signal_x86_64.c
+++ b/dlls/ntdll/signal_x86_64.c
@@ -2684,6 +2684,7 @@ PRUNTIME_FUNCTION WINAPI RtlLookupFunctionEntry( ULONG64 pc, ULONG64 *base, UNWI
     func = lookup_function_info( pc, base, &module );
     if (!func)
     {
+        *base = 0;
         if (module)
             WARN( "no exception table found in module %p pc %lx\n", module->BaseAddress, pc );
         else
diff --git a/dlls/ntdll/tests/exception.c b/dlls/ntdll/tests/exception.c
index 817a19c454e..8a80928954e 100644
--- a/dlls/ntdll/tests/exception.c
+++ b/dlls/ntdll/tests/exception.c
@@ -1487,8 +1487,8 @@ static void test_dynamic_unwind(void)
     func = pRtlLookupFunctionEntry( (ULONG_PTR)code_mem + code_offset + 16, &base, NULL );
     ok( func == NULL,
         "RtlLookupFunctionEntry returned unexpected function, expected: NULL, got: %p\n", func );
-    ok( base == 0xdeadbeef,
-        "RtlLookupFunctionEntry modified base address, expected: 0xdeadbeef, got: %lx\n", base );
+    ok( !base || broken(base == 0xdeadbeef),
+        "RtlLookupFunctionEntry modified base address, expected: 0, got: %lx\n", base );
 
     /* Test with pointer inside of our function */
     base = 0xdeadbeef;
@@ -1546,8 +1546,8 @@ static void test_dynamic_unwind(void)
     func = pRtlLookupFunctionEntry( (ULONG_PTR)code_mem + code_offset + 32, &base, NULL );
     ok( func == NULL,
         "RtlLookupFunctionEntry returned unexpected function, expected: NULL, got: %p\n", func );
-    ok( base == 0xdeadbeef,
-        "RtlLookupFunctionEntry modified base address, expected: 0xdeadbeef, got: %lx\n", base );
+    ok( !base || broken(base == 0xdeadbeef),
+        "RtlLookupFunctionEntry modified base address, expected: 0, got: %lx\n", base );
     ok( !count,
         "RtlLookupFunctionEntry issued %d unexpected calls to dynamic_unwind_callback\n", count );