diff --git a/sdrbase/dsp/cwkeyer.cpp b/sdrbase/dsp/cwkeyer.cpp
index 46729bd68..9e4384529 100644
--- a/sdrbase/dsp/cwkeyer.cpp
+++ b/sdrbase/dsp/cwkeyer.cpp
@@ -24,7 +24,7 @@
  * 1:  dash
  * -1: end of sequence
  */
-const char CWKeyer::m_asciiToMorse[128][7] = {
+const signed char CWKeyer::m_asciiToMorse[128][7] = {
         {-1,0,0,0,0,0,0}, // 0
         {-1,0,0,0,0,0,0}, // 1
         {-1,0,0,0,0,0,0}, // 2
diff --git a/sdrbase/dsp/cwkeyer.h b/sdrbase/dsp/cwkeyer.h
index 1b29aba02..1f81b6d07 100644
--- a/sdrbase/dsp/cwkeyer.h
+++ b/sdrbase/dsp/cwkeyer.h
@@ -94,7 +94,7 @@ private:
     CWKeyIambicState m_keyIambicState;
     CWTextState m_textState;
 
-    static const char m_asciiToMorse[128][7];
+    static const signed char m_asciiToMorse[128][7];
 
     void nextStateIambic();
     void nextStateText();