diff --git a/src/OpenFOAM/primitives/ints/int32/int32.H b/src/OpenFOAM/primitives/ints/int32/int32.H
index c2a3097ab6..2bf5e799d2 100644
--- a/src/OpenFOAM/primitives/ints/int32/int32.H
+++ b/src/OpenFOAM/primitives/ints/int32/int32.H
@@ -69,6 +69,15 @@ bool read(const char*, int32_t&);
 Istream& operator>>(Istream&, int32_t&);
 Ostream& operator<<(Ostream&, const int32_t);
 
+// On 32bit OSs long is not unambiguously int32_t (or int64_t) causing problems
+// for IO operator resolution.
+// This problem is avoided by explicitly defining the following operators:
+#if WM_ARCH_OPTION == 32
+    Istream& operator>>(Istream&, long&);
+    Ostream& operator<<(Ostream&, const long);
+#endif
+
+
 //- Template specialization for pTraits<int32_t>
 template<>
 class pTraits<int32_t>
diff --git a/src/OpenFOAM/primitives/ints/int32/int32IO.C b/src/OpenFOAM/primitives/ints/int32/int32IO.C
index d491e236a4..ae4a2a1d64 100644
--- a/src/OpenFOAM/primitives/ints/int32/int32IO.C
+++ b/src/OpenFOAM/primitives/ints/int32/int32IO.C
@@ -104,4 +104,18 @@ Foam::Ostream& Foam::operator<<(Ostream& os, const int32_t i)
 }
 
 
+#if WM_ARCH_OPTION == 32
+Foam::Istream& Foam::operator>>(Istream& is, long& i)
+{
+    return operator>>(is, reinterpret_cast<int32_t&>(i));
+}
+
+Foam::Ostream& Foam::operator<<(Ostream& os, const long i)
+{
+    os << int32_t(i);
+    return os;
+}
+#endif
+
+
 // ************************************************************************* //
diff --git a/wmake/rules/General/general b/wmake/rules/General/general
index ecbe83a14e..062c704f13 100644
--- a/wmake/rules/General/general
+++ b/wmake/rules/General/general
@@ -6,7 +6,8 @@ RANLIB     = ranlib
 CPP        = cpp
 LD         = ld
 
-GFLAGS     = -D$(WM_ARCH) -DWM_$(WM_PRECISION_OPTION) -DWM_LABEL_SIZE=$(WM_LABEL_SIZE)
+GFLAGS     = -D$(WM_ARCH) -DWM_ARCH_OPTION=$(WM_ARCH_OPTION) \
+             -DWM_$(WM_PRECISION_OPTION) -DWM_LABEL_SIZE=$(WM_LABEL_SIZE)
 GINC       =
 GLIBS      = -lm
 GLIB_LIBS  =