diff --git a/Makefile b/Makefile
index d74c55a..a10744e 100644
--- a/Makefile
+++ b/Makefile
@@ -8,20 +8,23 @@
 
 PG_CONFIG ?= pg_config
 
-SUBDIRS = bin lib
-
 # Pull out the version number from pg_config
 VERSION := $(shell $(PG_CONFIG) --version | awk '{print $$2}')
+ifeq ("$(VERSION)","")
+$(error pg_config not found)
+endif
 
-# version as a number, e.g. 9.1.4 -> 90104
-INTVERSION := $(shell echo $(VERSION) | sed -E 's/([0-9]+)\.([0-9]+)\.?([0-9]+)?(.*)/(\1*100+\2)*100+0\3/' | bc)
+# version as a number, e.g. 9.1.4 -> 901
+INTVERSION := $(shell echo $$(($$(echo $(VERSION) | sed -E 's/([0-9]+)\.([0-9]+).*/\1*100+\2/'))))
 
 # We support PostgreSQL 8.3 and later.
-ifeq ($(shell echo $$(($(INTVERSION) < 80300))),1)
+ifeq ($(shell echo $$(($(INTVERSION) < 803))),1)
 $(error pg_repack requires PostgreSQL 8.3 or later. This is $(VERSION))
 endif
 
 
+SUBDIRS = bin lib
+
 all install installdirs uninstall distprep clean distclean maintainer-clean debug:
 	@for dir in $(SUBDIRS); do \
 		$(MAKE) -C $$dir $@ || exit; \
diff --git a/bin/Makefile b/bin/Makefile
index 04f38f2..1193e5f 100644
--- a/bin/Makefile
+++ b/bin/Makefile
@@ -8,9 +8,9 @@
 
 PG_CONFIG ?= pg_config
 
-# version as a number, e.g. 9.1.4 -> 90104
+# version as a number, e.g. 9.1.4 -> 901
 VERSION := $(shell $(PG_CONFIG) --version | awk '{print $$2}')
-INTVERSION := $(shell echo $(VERSION) | sed -E 's/([0-9]+)\.([0-9]+)\.?([0-9]+)?.*/(\1*100+\2)*100+0\3/' | bc)
+INTVERSION := $(shell echo $$(($$(echo $(VERSION) | sed -E 's/([0-9]+)\.([0-9]+).*/\1*100+\2/'))))
 
 SRCS = pg_repack.c pgut/pgut.c pgut/pgut-fe.c
 OBJS = $(SRCS:.c=.o)
@@ -21,7 +21,7 @@ PROGRAM = pg_repack
 # Test suite
 #
 
-ifeq ($(shell echo $$(($(INTVERSION) >= 90100))),1)
+ifeq ($(shell echo $$(($(INTVERSION) >= 901))),1)
 REGRESS = init-extension
 else
 REGRESS = init-legacy
@@ -29,8 +29,8 @@ endif
 
 REGRESS += repack tablespace
 
-# This test depends on collate, not supported before 9.0
-ifeq ($(shell echo $$(($(INTVERSION) >= 90000))),1)
+# This test depends on collate, not supported before 9.1
+ifeq ($(shell echo $$(($(INTVERSION) >= 901))),1)
 REGRESS += issue3
 endif
 
diff --git a/lib/Makefile b/lib/Makefile
index 8698163..1035742 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,9 +8,9 @@
 
 PG_CONFIG ?= pg_config
 
-# version as a number, e.g. 9.1.4 -> 90104
+# version as a number, e.g. 9.1.4 -> 901
 VERSION := $(shell $(PG_CONFIG) --version | awk '{print $$2}')
-INTVERSION := $(shell echo $(VERSION) | sed -E 's/([0-9]+)\.([0-9]+)\.?([0-9]+)?.*/(\1*100+\2)*100+0\3/' | bc)
+INTVERSION := $(shell echo $$(($$(echo $(VERSION) | sed -E 's/([0-9]+)\.([0-9]+).*/\1*100+\2/'))))
 
 EXTENSION = pg_repack
 MODULE_big = $(EXTENSION)
@@ -24,7 +24,7 @@ REPACK_VERSION = $(shell grep '"version":' ../META.json | head -1 \
 PG_CPPFLAGS = -DREPACK_VERSION=$(REPACK_VERSION)
 
 # Support CREATE EXTENSION for PG >= 9.1 and a simple sql script for PG < 9.1
-ifeq ($(shell echo $$(($(INTVERSION) >= 90100))),1)
+ifeq ($(shell echo $$(($(INTVERSION) >= 901))),1)
 DATA_built = pg_repack--$(REPACK_VERSION).sql pg_repack.control
 else
 DATA_built = pg_repack.sql