diff --git a/panama.cpp b/panama.cpp
index 7238f6c8..06ef25aa 100644
--- a/panama.cpp
+++ b/panama.cpp
@@ -463,7 +463,7 @@ void PanamaCipherPolicy<B>::CipherResynchronize(byte *keystreamBuffer, const byt
 	}
 
 #if CRYPTOPP_BOOL_SSE2_ASM_AVAILABLE || defined(CRYPTOPP_X64_MASM_AVAILABLE)
-	if (B::ToEnum() == LITTLE_ENDIAN_ORDER && HasSSE2())
+	if (B::ToEnum() == LITTLE_ENDIAN_ORDER && HasSSE2() && !IsP4())		// SSE2 code is slower on P4 Prescott
 		Panama_SSE2_Pull(32, this->m_state, NULL, NULL);
 	else
 #endif