diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 301ce3b..ae6ba71 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -5856,6 +5856,9 @@
         zSig1 = 0;
         zSig0 = aSig + bSig;
         if ( aExp == 0 ) {
+            if (zSig0 == 0) {
+                return packFloatx80(zSign, 0, 0);
+            }
             normalizeFloatx80Subnormal( zSig0, &zExp, &zSig0 );
             goto roundAndPack;
         }