diff --git a/radio/Interpolation.hpp b/radio/Interpolation.hpp
index a234d87..172a970 100644
--- a/radio/Interpolation.hpp
+++ b/radio/Interpolation.hpp
@@ -316,19 +316,23 @@ public:
 	{
 		uint32_t i;
 		uint32_t j;
-		ComplexScalar res(0,0);
 		
 		j = 0;
 		for (i=0; i < len; i++)
 		{
 			m_pFir[m_currStage].feed(src(i));
-			res += m_pFir[m_currStage].processReal(m_pCoeff[m_currStage]);
-			m_currStage--;
-			if (m_currStage >= m_M)
+			if (m_currStage == (m_M-1))
+			{
+				dst(j) = m_pFir[m_currStage].processReal(m_pCoeff[m_currStage]);
+			}
+			else
+			{
+				dst(j) += m_pFir[m_currStage].processReal(m_pCoeff[m_currStage]);
+			}
+			if (--m_currStage >= m_M)
 			{
-				dst(j++) = res;
-				res = ComplexScalar(0,0);
 				m_currStage = m_M-1;
+				j++;
 			}
 			
 		}