diff --git a/inc/GSLBuilder.pm b/inc/GSLBuilder.pm
index 6977c7c..dac3ab0 100644
--- a/inc/GSLBuilder.pm
+++ b/inc/GSLBuilder.pm
@@ -207,6 +207,12 @@ sub compile_swig {
     my @swig_flags = defined($p->{swig_flags}) ? $self->split_like_shell($p->{swig_flags}) : ();
     push @swig_flags, "-I./include";
     my ($major, $minor, $numerical_ver) = reformat_version($ver);
+    if ($numerical_ver =~ /^0+$/) {
+        die "Unexpected swig version: $ver";
+    }
+    else {
+        $numerical_ver =~ s/^0+//;  # Swig seems to have problems with leading zeros
+    }
     push @swig_flags, "-DMG_GSL_MAJOR_VERSION=$major",
       "-DMG_GSL_MINOR_VERSION=$minor",
       "-DMG_GSL_VERSION=\"$major.$minor\"",
diff --git a/swig/SparseMatrix.i b/swig/SparseMatrix.i
index 5442473..50005be 100644
--- a/swig/SparseMatrix.i
+++ b/swig/SparseMatrix.i
@@ -9,7 +9,13 @@
     #include "gsl/gsl_spmatrix.h"
 %}
 
-#if MG_GSL_NUM_VERSION >= 002006
+#if MG_GSL_NUM_VERSION >= 2006
+%warn "Including new GSL headers";
+#else
+%warn "Including legacy GSL headers";
+#endif
+
+#if MG_GSL_NUM_VERSION >= 2006
 // ignore gsl_spmatrix_uchar_norm1, gsl_spmatrix_char_norm1, ...
   %rename("%(regex:/^gsl_spmatrix_u.*_norm1$/$ignore/)s") "";
   %include "gsl/gsl_spmatrix.h"