diff --git a/dlls/rsaenh/rsaenh.c b/dlls/rsaenh/rsaenh.c
index 02e3e6e32b..eafc92c960 100644
--- a/dlls/rsaenh/rsaenh.c
+++ b/dlls/rsaenh/rsaenh.c
@@ -1940,12 +1940,20 @@ BOOL WINAPI RSAENH_CPEncrypt(HCRYPTPROV hProv, HCRYPTKEY hKey, HCRYPTHASH hHash,
             memcpy(in, out, pCryptKey->dwBlockLen); 
         }
     } else if (GET_ALG_TYPE(pCryptKey->aiAlgid) == ALG_TYPE_STREAM) {
+        if (pbData == NULL) {
+            *pdwDataLen = dwBufLen;
+            return TRUE;
+        }
         encrypt_stream_impl(pCryptKey->aiAlgid, &pCryptKey->context, pbData, *pdwDataLen);
     } else if (GET_ALG_TYPE(pCryptKey->aiAlgid) == ALG_TYPE_RSA) {
         if (pCryptKey->aiAlgid == CALG_RSA_SIGN) {
             SetLastError(NTE_BAD_KEY);
             return FALSE;
         }
+        if (!pbData) {
+            *pdwDataLen = pCryptKey->dwBlockLen;
+            return TRUE;
+        }
         if (dwBufLen < pCryptKey->dwBlockLen) {
             SetLastError(ERROR_MORE_DATA);
             return FALSE;
diff --git a/dlls/rsaenh/tests/rsaenh.c b/dlls/rsaenh/tests/rsaenh.c
index 01cbb0c941..90caeb4923 100644
--- a/dlls/rsaenh/tests/rsaenh.c
+++ b/dlls/rsaenh/tests/rsaenh.c
@@ -303,6 +303,11 @@ static void test_block_cipher_modes(void)
     result = CryptSetKeyParam(hKey, KP_MODE, (BYTE*)&dwMode, 0);
     ok(result, "%08lx\n", GetLastError());
 
+    dwLen = 23;
+    result = CryptEncrypt(hKey, (HCRYPTHASH)NULL, TRUE, 0, NULL, &dwLen, 24);
+    ok(result, "CryptEncrypt failed: %08lx\n", GetLastError());
+    ok(dwLen == 24, "Unexpected length %ld\n", dwLen);
+
     SetLastError(ERROR_SUCCESS);
     dwLen = 23;
     result = CryptEncrypt(hKey, (HCRYPTHASH)NULL, TRUE, 0, abData, &dwLen, 24);
@@ -317,6 +322,11 @@ static void test_block_cipher_modes(void)
     result = CryptSetKeyParam(hKey, KP_MODE, (BYTE*)&dwMode, 0);
     ok(result, "%08lx\n", GetLastError());
     
+    dwLen = 23;
+    result = CryptEncrypt(hKey, (HCRYPTHASH)NULL, TRUE, 0, NULL, &dwLen, 24);
+    ok(result, "CryptEncrypt failed: %08lx\n", GetLastError());
+    ok(dwLen == 24, "Unexpected length %ld\n", dwLen);
+
     dwLen = 23;
     result = CryptEncrypt(hKey, (HCRYPTHASH)NULL, TRUE, 0, abData, &dwLen, 24);
     ok(result && dwLen == 24 && !memcmp(cbc, abData, sizeof(cbc)), 
@@ -595,6 +605,9 @@ static void test_rc4(void)
         result = CryptDestroyHash(hHash);
         ok(result, "%08lx\n", GetLastError());
 
+        dwDataLen = 16;
+        result = CryptEncrypt(hKey, (HCRYPTHASH)NULL, TRUE, 0, NULL, &dwDataLen, 24);
+        ok(result, "%08lx\n", GetLastError());
         dwDataLen = 16;
         result = CryptEncrypt(hKey, (HCRYPTHASH)NULL, TRUE, 0, pbData, &dwDataLen, 24);
         ok(result, "%08lx\n", GetLastError());
@@ -1104,6 +1117,10 @@ static void test_rsa_encrypt(void)
     ok (result, "%08lx\n", GetLastError());
     if (!result) return;
 
+    dwLen = 12;
+    result = CryptEncrypt(hRSAKey, 0, TRUE, 0, NULL, &dwLen, (DWORD)sizeof(abData));
+    ok(result, "CryptEncrypt failed: %08lx\n", GetLastError());
+    ok(dwLen == 128, "Unexpected length %ld\n", dwLen);
     dwLen = 12;
     result = CryptEncrypt(hRSAKey, 0, TRUE, 0, abData, &dwLen, (DWORD)sizeof(abData));
     ok (result, "%08lx\n", GetLastError());