diff --git a/src/common_audio/signal_processing/include/spl_inl_armv7.h b/src/common_audio/signal_processing/include/spl_inl_armv7.h
index 2eff496b8..8461474fb 100644
--- a/src/common_audio/signal_processing/include/spl_inl_armv7.h
+++ b/src/common_audio/signal_processing/include/spl_inl_armv7.h
@@ -64,6 +64,7 @@ static __inline WebRtc_Word32 WEBRTC_SPL_MUL_16_16(WebRtc_Word16 a,
   return tmp;
 }
 
+// TODO(kma): add unit test.
 static __inline int32_t WebRtc_MulAccumW16(int16_t a,
                                           int16_t b,
                                           int32_t c) {
@@ -124,7 +125,12 @@ static __inline WebRtc_Word16 WebRtcSpl_GetSizeInBits(WebRtc_UWord32 n) {
 static __inline int WebRtcSpl_NormW32(WebRtc_Word32 a) {
   WebRtc_Word32 tmp = 0;
 
-  if (a <= 0) a ^= 0xFFFFFFFF;
+  if (a == 0) {
+    return 0;
+  }
+  else if (a < 0) {
+    a ^= 0xFFFFFFFF;
+  }
 
   __asm __volatile ("clz %0, %1":"=r"(tmp):"r"(a));
 
@@ -144,13 +150,19 @@ static __inline int WebRtcSpl_NormU32(WebRtc_UWord32 a) {
 static __inline int WebRtcSpl_NormW16(WebRtc_Word16 a) {
   WebRtc_Word32 tmp = 0;
 
-  if (a <= 0) a ^= 0xFFFFFFFF;
+  if (a == 0) {
+    return 0;
+  }
+  else if (a < 0) {
+    a ^= 0xFFFFFFFF;
+  }
 
   __asm __volatile ("clz %0, %1":"=r"(tmp):"r"(a));
 
   return tmp - 17;
 }
 
+// TODO(kma): add unit test.
 static __inline WebRtc_Word16 WebRtcSpl_SatW32ToW16(WebRtc_Word32 value32) {
   WebRtc_Word16 out16 = 0;
 
@@ -158,4 +170,5 @@ static __inline WebRtc_Word16 WebRtcSpl_SatW32ToW16(WebRtc_Word32 value32) {
 
   return out16;
 }
+
 #endif  // WEBRTC_SPL_SPL_INL_ARMV7_H_
diff --git a/src/common_audio/signal_processing/signal_processing_unittest.cc b/src/common_audio/signal_processing/signal_processing_unittest.cc
index e20ed74e8..d5026fb88 100644
--- a/src/common_audio/signal_processing/signal_processing_unittest.cc
+++ b/src/common_audio/signal_processing/signal_processing_unittest.cc
@@ -138,8 +138,20 @@ TEST_F(SplTest, InlineTest) {
     char bVersion[8];
 
     EXPECT_EQ(17, WebRtcSpl_GetSizeInBits(a32));
+
+    EXPECT_EQ(0, WebRtcSpl_NormW32(0));
+    EXPECT_EQ(31, WebRtcSpl_NormW32(-1));
+    EXPECT_EQ(0, WebRtcSpl_NormW32(WEBRTC_SPL_WORD32_MIN));
     EXPECT_EQ(14, WebRtcSpl_NormW32(a32));
+
+    EXPECT_EQ(0, WebRtcSpl_NormW16(0));
+    EXPECT_EQ(15, WebRtcSpl_NormW16(-1));
+    EXPECT_EQ(0, WebRtcSpl_NormW16(WEBRTC_SPL_WORD16_MIN));
     EXPECT_EQ(4, WebRtcSpl_NormW16(b32));
+
+    EXPECT_EQ(0, WebRtcSpl_NormU32(0));
+    EXPECT_EQ(0, WebRtcSpl_NormU32(-1));
+    EXPECT_EQ(0, WebRtcSpl_NormU32(WEBRTC_SPL_WORD32_MIN));
     EXPECT_EQ(15, WebRtcSpl_NormU32(a32));
 
     EXPECT_EQ(104, WebRtcSpl_AddSatW16(a16, b16));
@@ -147,6 +159,7 @@ TEST_F(SplTest, InlineTest) {
 
     EXPECT_EQ(109410, WebRtcSpl_AddSatW32(a32, b32));
     EXPECT_EQ(112832, WebRtcSpl_SubSatW32(a32, b32));
+
     a32 = 0x80000000;
     b32 = 0x80000000;
     // Cast to signed int to avoid compiler complaint on gtest.h.