diff --git a/src/Makefile b/src/Makefile
index d105da4a..b812168a 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2,10 +2,10 @@
 #
 # usage:
 #   `make target=linux'         # linux
-#   `make target=djggp2'        # djggp2
-#   `make target=cygwin'        # cygwin
+#   `make target=djggp2'        # djggp2 2.03
+#   `make target=cygwin'        # cygwin 1.1.x
 #   `make target=mingw32'       # mingw32
-#   `make target=no-cygwin'     # mingw32 as included in cygwin
+#   `make target=no-cygwin'     # mingw32 as included in cygwin 1.1.x
 #   `make target=vc6'           # Visual C++ 6.0
 #
 
@@ -44,7 +44,7 @@ ifneq ($(strip $(wildcard /platform/sun4?/kernel/unix)),)
 target = sparc
 endif
 ifeq ($(target),msc)
-target = vc6
+override target = vc6
 endif
 
 
@@ -201,6 +201,7 @@ endif	# djgpp2
 ifeq ($(target),cygwin)
 CFLAGS_M += -mno-schedule-prologue
 CFLAGS_M += -march=i386 -mcpu=pentium
+CFLAGS_WERROR = -Werror
 endif
 
 ifeq ($(target),mingw32)
@@ -213,6 +214,7 @@ ifeq ($(target),no-cygwin)
 CC = gcc -mno-cygwin
 CFLAGS_M += -mno-schedule-prologue
 CFLAGS_M += -march=i386 -mcpu=pentium
+CFLAGS_WERROR = -Werror
 endif
 
 
diff --git a/src/p_lx_elf.cpp b/src/p_lx_elf.cpp
index f63d756b..95d4bf73 100644
--- a/src/p_lx_elf.cpp
+++ b/src/p_lx_elf.cpp
@@ -361,7 +361,7 @@ void PackLinuxI386elf::pack(OutputFile *fo)
     updateLoader(fo);
 
     // finally check compression ratio
-    if (!super::checkCompressionRatio(fo->getBytesWritten(), ph.u_len))
+    if (!super::checkCompressionRatio(ph.u_len, fo->getBytesWritten()))
         throwNotCompressible();
 }
 
diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index 5f10368a..e17e88d4 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -197,7 +197,7 @@ void PackUnix::pack(OutputFile *fo)
     updateLoader(fo);
 
     // finally check compression ratio
-    if (!Packer::checkCompressionRatio(fo->getBytesWritten(), ph.u_len))
+    if (!Packer::checkCompressionRatio(ph.u_len, fo->getBytesWritten()))
         throwNotCompressible();
 }
 
diff --git a/src/p_w32pe.cpp b/src/p_w32pe.cpp
index 6d0b56bc..19a6efa0 100644
--- a/src/p_w32pe.cpp
+++ b/src/p_w32pe.cpp
@@ -1915,7 +1915,7 @@ void PackW32Pe::pack(OutputFile *fo)
     copyOverlay(fo, overlay, &obuf);
 
     // finally check compresion ratio
-    if (!checkCompressionRatio(fo->getBytesWritten(), file_size))
+    if (!checkCompressionRatio(file_size, fo->getBytesWritten()))
         throwNotCompressible();
 }
 
diff --git a/src/packer.cpp b/src/packer.cpp
index 1aa24621..eee19c5c 100644
--- a/src/packer.cpp
+++ b/src/packer.cpp
@@ -222,7 +222,7 @@ bool Packer::compress(upx_bytep in, upx_bytep out,
     uip->endCallback();
 
     //printf("Packer::compress: %d/%d: %7d -> %7d\n", ph.method, ph.level, ph.u_len, ph.c_len);
-    if (!checkCompressionRatio(ph.c_len, ph.u_len))
+    if (!checkCompressionRatio(ph.u_len, ph.c_len))
         return false;
     // return in any case if not compressible
     if (ph.c_len >= ph.u_len)
@@ -249,8 +249,12 @@ bool Packer::compress(upx_bytep in, upx_bytep out,
 }
 
 
-bool Packer::checkCompressionRatio(unsigned c_len, unsigned u_len) const
+bool Packer::checkCompressionRatio(unsigned u_len, unsigned c_len) const
 {
+    assert((int)u_len > 0);
+    assert((int)c_len > 0);
+    assert((off_t)u_len < file_size);
+
 #if 1
     if (c_len >= u_len - u_len / 8)         // min. 12.5% gain
         return false;
@@ -1133,7 +1137,7 @@ void Packer::compressWithFilters(Filter *parm_ft, unsigned *parm_overlapoh,
     // finally check compression ratio
     if (best_ph.c_len + best_ph_lsize >= best_ph.u_len)
         throwNotCompressible();
-    if (!checkCompressionRatio(best_ph.c_len, best_ph.u_len))
+    if (!checkCompressionRatio(best_ph.u_len, best_ph.c_len))
         throwNotCompressible();
 
     // convenience
diff --git a/src/packer.h b/src/packer.h
index 0a76c98b..4911b580 100644
--- a/src/packer.h
+++ b/src/packer.h
@@ -148,7 +148,7 @@ protected:
                           unsigned max_offset = 0, unsigned max_match = 0);
     virtual void decompress(const upx_bytep in,
                             upx_bytep out, bool verify_checksum=true);
-    virtual bool checkCompressionRatio(unsigned c_len, unsigned u_len) const;
+    virtual bool checkCompressionRatio(unsigned u_len, unsigned c_len) const;
 
     // high-level compression drivers
     void compressWithFilters(Filter *ft, unsigned *overlapoh,