diff --git a/chacha.cpp b/chacha.cpp
index a89fa016..05075b17 100644
--- a/chacha.cpp
+++ b/chacha.cpp
@@ -25,6 +25,8 @@ extern void ChaCha_OperateKeystream_AVX2(const word32 *state, const byte* input,
 #endif
 
 #if (CRYPTOPP_ALTIVEC_AVAILABLE)
+// ChaCha_OperateKeystream_POWER7 may be compiled with either -mcpu=power7 or
+// -mcpu=power4. The makefile drops to POWER4 if POWER7 is not available.
 extern void ChaCha_OperateKeystream_POWER7(const word32 *state, const byte* input, byte *output, unsigned int rounds);
 #endif
 
@@ -85,8 +87,7 @@ std::string ChaCha_Policy::AlgorithmProvider() const
     if (HasPower7())
         return "Power7";
     else
-#endif
-#if (CRYPTOPP_ALTIVEC_AVAILABLE)
+#elif (CRYPTOPP_ALTIVEC_AVAILABLE)
     if (HasAltivec())
         return "Altivec";
     else
@@ -250,11 +251,31 @@ void ChaCha_Policy::OperateKeystream(KeystreamOperation operation,
         }
 #endif
 
-#if (CRYPTOPP_ALTIVEC_AVAILABLE)
+#if (CRYPTOPP_POWER7_AVAILABLE)
+        if (HasPower7())
+        {
+            while (iterationCount >= 4 && MultiBlockSafe(4))
+            {
+                // ChaCha_OperateKeystream_POWER7 compiled with -mcpu=power7 and -DCRYPTOPP_POWER7_AVAILABLE
+                const bool xorInput = (operation & INPUT_NULL) != INPUT_NULL;
+                ChaCha_OperateKeystream_POWER7(m_state, xorInput ? input : NULLPTR, output, m_rounds);
+
+                // MultiBlockSafe avoids overflow on the counter words
+                m_state[12] += 4;
+                //if (m_state[12] < 4)
+                //    m_state[13]++;
+
+                input += (!!xorInput)*4*BYTES_PER_ITERATION;
+                output += 4*BYTES_PER_ITERATION;
+                iterationCount -= 4;
+            }
+        }
+#elif (CRYPTOPP_ALTIVEC_AVAILABLE)
         if (HasAltivec())
         {
             while (iterationCount >= 4 && MultiBlockSafe(4))
             {
+                // ChaCha_OperateKeystream_POWER7 compiled with -mcpu=power4 and -DCRYPTOPP_ALTIVEC_AVAILABLE
                 const bool xorInput = (operation & INPUT_NULL) != INPUT_NULL;
                 ChaCha_OperateKeystream_POWER7(m_state, xorInput ? input : NULLPTR, output, m_rounds);