diff --git a/rostests/apitests/crt/_vscprintf.c b/rostests/apitests/crt/_vscprintf.c
index c3717abaa6a..1a72bd689e1 100644
--- a/rostests/apitests/crt/_vscprintf.c
+++ b/rostests/apitests/crt/_vscprintf.c
@@ -7,6 +7,7 @@
 #include <stdio.h>
 #include <wine/test.h>
 #include <tchar.h>
+#include <errno.h>
 
 static void call_varargs(int expected_ret, LPCSTR formatString, ...)
 {
@@ -26,4 +27,5 @@ START_TEST(_vscprintf)
     call_varargs(11, "%u cookies", 100);
     /* Test NULL argument */
     call_varargs(-1, NULL);
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
 }
diff --git a/rostests/apitests/crt/_vscwprintf.c b/rostests/apitests/crt/_vscwprintf.c
index 0c35e2a5b77..d2390b7876c 100644
--- a/rostests/apitests/crt/_vscwprintf.c
+++ b/rostests/apitests/crt/_vscwprintf.c
@@ -7,6 +7,7 @@
 #include <stdio.h>
 #include <wine/test.h>
 #include <tchar.h>
+#include <errno.h>
 
 static void call_varargs(int expected_ret, LPCWSTR formatString, ...)
 {
@@ -27,4 +28,7 @@ START_TEST(_vscwprintf)
     
     /* Test NULL argument */
     call_varargs(-1, NULL);
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
+#endif
 }
diff --git a/rostests/apitests/crt/_vsnprintf.c b/rostests/apitests/crt/_vsnprintf.c
index 739b2c9d48f..e7657c3c98b 100644
--- a/rostests/apitests/crt/_vsnprintf.c
+++ b/rostests/apitests/crt/_vsnprintf.c
@@ -40,6 +40,9 @@ START_TEST(_vsnprintf)
     EndSeh(STATUS_ACCESS_VIOLATION);
 #else
     EndSeh(STATUS_SUCCESS);
+#endif
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
 #endif
     /* This one is no better */
     StartSeh()
@@ -48,6 +51,9 @@ START_TEST(_vsnprintf)
     EndSeh(STATUS_ACCESS_VIOLATION);
 #else
     EndSeh(STATUS_SUCCESS);
+#endif
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
 #endif
     /* One more NULL checks */
     StartSeh()
@@ -57,4 +63,7 @@ START_TEST(_vsnprintf)
 #else
     EndSeh(STATUS_SUCCESS);
 #endif
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
+#endif
 }
diff --git a/rostests/apitests/crt/_vsnwprintf.c b/rostests/apitests/crt/_vsnwprintf.c
index 042e0f00ce8..e37616cc9fb 100644
--- a/rostests/apitests/crt/_vsnwprintf.c
+++ b/rostests/apitests/crt/_vsnwprintf.c
@@ -40,6 +40,9 @@ START_TEST(_vsnwprintf)
     EndSeh(STATUS_ACCESS_VIOLATION);
 #else
     EndSeh(STATUS_SUCCESS);
+#endif
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
 #endif
     /* This one is no better */
     StartSeh()
@@ -48,6 +51,9 @@ START_TEST(_vsnwprintf)
     EndSeh(STATUS_ACCESS_VIOLATION);
 #else
     EndSeh(STATUS_SUCCESS);
+#endif
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
 #endif
     /* One more NULL checks */
     StartSeh()
@@ -57,4 +63,7 @@ START_TEST(_vsnwprintf)
 #else
     EndSeh(STATUS_SUCCESS);
 #endif
+#if defined(TEST_MSVCRT) /* NTDLL doesn't use/set errno */
+    ok(errno == EINVAL, "Expected EINVAL, got %u\n", errno);
+#endif
 }