1 files changed, 4 insertions, 1 deletions

diff --git a/crypto/src/crypto/modes/GOFBBlockCipher.cs b/crypto/src/crypto/modes/GOFBBlockCipher.cs

index 4299f11a9..436b58a1d 100644
--- a/crypto/src/crypto/modes/GOFBBlockCipher.cs
+++ b/crypto/src/crypto/modes/GOFBBlockCipher.cs
@@ -171,7 +171,10 @@ namespace Org.BouncyCastle.Crypto.Modes
 			N4 += C1;
             if (N4 < C1)  // addition is mod (2**32 - 1)
             {
-                N4++;
+                if (N4 > 0)
+                {
+                    N4++;
+                }
             }
             intTobytes(N3, ofbV, 0);
 			intTobytes(N4, ofbV, 4);