diff --git a/Makefile.OpenSSL.inc b/Makefile.OpenSSL.inc
new file mode 100644
index 00000000..76f3e85c
--- /dev/null
+++ b/Makefile.OpenSSL.inc
@@ -0,0 +1,2 @@
+CRYPTO_CSOURCES = openssl.c
+CRYPTO_HHEADERS = openssl.h
diff --git a/Makefile.am b/Makefile.am
index 023200d0..e0a74c73 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -75,6 +75,8 @@ gen-coverage:
 coverage: init-coverage build-coverage gen-coverage
 
 # DSP/VCPROJ generation adapted from libcurl
+# only OpenSSL is supported with this build system
+include Makefile.OpenSSL.inc
 # Makefile.inc provides the CSOURCES and HHEADERS defines
 include Makefile.inc
 
diff --git a/Makefile.inc b/Makefile.inc
index b2e0f78d..8f2e570c 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -1,18 +1,6 @@
 CSOURCES = channel.c comp.c crypt.c hostkey.c kex.c mac.c misc.c \
  packet.c publickey.c scp.c session.c sftp.c userauth.c transport.c \
- version.c knownhost.c agent.c pem.c keepalive.c global.c
-if OPENSSL
-CSOURCES += openssl.c
-endif
-if LIBGCRYPT
-CSOURCES += libgcrypt.c
-endif
+ version.c knownhost.c agent.c $(CRYPTO_CSOURCES) pem.c keepalive.c global.c
 
-HHEADERS = libssh2_priv.h transport.h channel.h comp.h mac.h misc.h \
- packet.h userauth.h session.h sftp.h crypto.h
-if OPENSSL
-HHEADERS += openssl.h
-endif
-if LIBGCRYPT
-HHEADERS += libgcrypt.h
-endif
+HHEADERS = libssh2_priv.h $(CRYPTO_HHEADERS) transport.h channel.h comp.h \
+ mac.h misc.h packet.h userauth.h session.h sftp.h crypto.h
diff --git a/Makefile.libgcrypt.inc b/Makefile.libgcrypt.inc
new file mode 100644
index 00000000..5d56292c
--- /dev/null
+++ b/Makefile.libgcrypt.inc
@@ -0,0 +1,2 @@
+CRYPTO_CSOURCES = libgcrypt.c
+CRYPTO_HHEADERS = libgcrypt.h
diff --git a/NMakefile b/NMakefile
index f3fcce11..b15fd2ec 100644
--- a/NMakefile
+++ b/NMakefile
@@ -1,5 +1,7 @@
 !include "win32/config.mk"
 
+# only OpenSSL is supported with this build system
+!include "Makefile.OpenSSL.inc"
 !include "Makefile.inc"
 
 OBJECTS=$(CSOURCES:.c=.obj)
diff --git a/nw/GNUmakefile b/nw/GNUmakefile
index 2e24c883..e666e29f 100644
--- a/nw/GNUmakefile
+++ b/nw/GNUmakefile
@@ -213,6 +213,9 @@ endif
 
 vpath %.c . ../src
 
+# only OpenSSL is supported with this build system
+include ../Makefile.OpenSSL.inc
+
 # include Makefile.inc to get CSOURCES define
 include ../Makefile.inc
 
diff --git a/src/Makefile.am b/src/Makefile.am
index 53fb4e8b..da7beb5b 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,6 +1,14 @@
 # $Id: Makefile.am,v 1.21 2009/05/07 17:21:56 bagder Exp $
 AUTOMAKE_OPTIONS = foreign nostdinc
 
+# Get the CRYPTO_CSOURCES and CRYPTO_HHEADERS defines
+if OPENSSL
+include ../Makefile.OpenSSL.inc
+endif
+if LIBGCRYPT
+include ../Makefile.libgcrypt.inc
+endif
+
 # Makefile.inc provides the CSOURCES and HHEADERS defines
 include ../Makefile.inc
 
diff --git a/win32/GNUmakefile b/win32/GNUmakefile
index 5dcd3c8f..c0cc20ac 100644
--- a/win32/GNUmakefile
+++ b/win32/GNUmakefile
@@ -179,6 +179,9 @@ CFLAGS	+= $(INCLUDES)
 
 vpath %.c . ../src
 
+# only OpenSSL is supported with this build system
+include ../Makefile.OpenSSL.inc
+
 # include Makefile.inc to get CSOURCES define
 include ../Makefile.inc
 
diff --git a/win32/Makefile.Watcom b/win32/Makefile.Watcom
index 3393ad43..5847cf73 100644
--- a/win32/Makefile.Watcom
+++ b/win32/Makefile.Watcom
@@ -93,6 +93,8 @@ LIB_ARG  = $(OBJ_BASE)\stat\wlib.arg
 !ifndef %MAKEFLAGS
 !error You MUST call wmake with the -u switch!
 !else
+# only OpenSSL is supported with this build system
+!include ..\Makefile.OpenSSL.inc
 !include ..\Makefile.inc
 !endif