diff --git a/core/src/main/java/org/bouncycastle/crypto/io/CipherInputStream.java b/core/src/main/java/org/bouncycastle/crypto/io/CipherInputStream.java
index 93b04e9934..66772df593 100644
--- a/core/src/main/java/org/bouncycastle/crypto/io/CipherInputStream.java
+++ b/core/src/main/java/org/bouncycastle/crypto/io/CipherInputStream.java
@@ -46,7 +46,9 @@ public CipherInputStream(
 
         this.bufferedBlockCipher = cipher;
 
-        buf = new byte[cipher.getOutputSize(INPUT_BUF_SIZE)];
+        int outSize = cipher.getOutputSize(INPUT_BUF_SIZE);
+
+        buf = new byte[(outSize > INPUT_BUF_SIZE) ? outSize : INPUT_BUF_SIZE];
         inBuf = new byte[INPUT_BUF_SIZE];
     }
 
@@ -71,7 +73,9 @@ public CipherInputStream(InputStream is, AEADBlockCipher cipher)
 
         this.aeadBlockCipher = cipher;
 
-        buf = new byte[cipher.getOutputSize(INPUT_BUF_SIZE)];
+        int outSize = cipher.getOutputSize(INPUT_BUF_SIZE);
+
+        buf = new byte[(outSize > INPUT_BUF_SIZE) ? outSize : INPUT_BUF_SIZE];
         inBuf = new byte[INPUT_BUF_SIZE];
     }