diff --git a/include/wx/math.h b/include/wx/math.h
index 8f5e9ddc56..261969d364 100644
--- a/include/wx/math.h
+++ b/include/wx/math.h
@@ -150,6 +150,9 @@ inline int wxRound(double x)
 inline double wxDegToRad(double deg) { return (deg * M_PI) / 180.0; }
 inline double wxRadToDeg(double rad) { return (rad * 180.0) / M_PI; }
 
+// Count trailing zeros.
+WXDLLIMPEXP_BASE unsigned int wxCTZ(wxUint32 x);
+
 #endif /* __cplusplus */
 
 
@@ -181,14 +184,4 @@ inline double wxRadToDeg(double rad) { return (rad * 180.0) / M_PI; }
 /* Compute the greatest common divisor of two positive integers */
 WXDLLIMPEXP_BASE unsigned int wxGCD(unsigned int u, unsigned int v);
 
-#ifdef __cplusplus
-/* Count trailing zeros
-
-Returns the number of trailing zeros in unsigned input x.
-
-@since 3.1.2
-*/
-WXDLLIMPEXP_BASE unsigned int wxCTZ(unsigned x);
-#endif
-
 #endif /* _WX_MATH_H_ */
diff --git a/interface/wx/math.h b/interface/wx/math.h
index ca11a9fff2..b1486c270c 100644
--- a/interface/wx/math.h
+++ b/interface/wx/math.h
@@ -75,6 +75,19 @@ double wxDegToRad(double deg);
  */
 double wxRadToDeg(double rad);
 
+/**
+    Count the number of trailing zeros.
+
+    This function returns the number of trailing zeros in the binary notation
+    of its argument @a x. E.g. for @a x equal to 4, or 0b100, the return value
+    is 2.
+
+    @param x Strictly positive, i.e. non-zero, 32 bit number.
+
+    @since 3.1.2
+ */
+unsigned int wxCTZ(wxUint32 x);
+
 /**
     Small wrapper around round().
 */
diff --git a/src/common/utilscmn.cpp b/src/common/utilscmn.cpp
index 23324e28e6..456dc1b38a 100644
--- a/src/common/utilscmn.cpp
+++ b/src/common/utilscmn.cpp
@@ -1021,7 +1021,7 @@ unsigned int wxGCD(unsigned int u, unsigned int v)
 // wxCTZ
 // Count trailing zeros. Use optimised builtin where available.
 // ----------------------------------------------------------------------------
-unsigned int wxCTZ(unsigned x)
+unsigned int wxCTZ(wxUint32 x)
 {
     wxCHECK_MSG(x > 0, 0, "Undefined for x == 0.");
 #ifdef __GNUC__