diff --git a/doc/building on MS Windows.txt b/doc/building on MS Windows.txt
index bb15e1f05..4df3ddd22 100644
--- a/doc/building on MS Windows.txt	
+++ b/doc/building on MS Windows.txt	
@@ -214,7 +214,7 @@ a suitable location like ~/build and change working directory to it:
 Configure and build and install the library in a suitable place (I use
 ~/local as a root directory for installed packages.
 
-    ~/src/portaudio/configure --prefix=$(HOME)/local/portaudio/mingw64 \
+    ~/src/portaudio/configure --prefix=$HOME/local/portaudio/mingw64 \
        --with-winapi=wmme,directx,wdmks --disable-static --enable-shared CFLAGS=-DNDEBUG
     make && make install
 
diff --git a/validators/CallsignValidator.cpp b/validators/CallsignValidator.cpp
index d6e1bb2c9..d6aba538c 100644
--- a/validators/CallsignValidator.cpp
+++ b/validators/CallsignValidator.cpp
@@ -14,7 +14,7 @@ auto CallsignValidator::validate (QString& input, int& pos) const -> State
       input.remove (0, 1);
       if (pos > 0) --pos;
     }
-  while (input.size () && input[input.size ()].isSpace ())
+  while (input.size () && input[input.size () - 1].isSpace ())
     {
       if (pos > input.size ()) --pos;
       input.chop (1);