diff --git a/Makefile b/Makefile
index c862176005..a6d5474af2 100644
--- a/Makefile
+++ b/Makefile
@@ -17,8 +17,8 @@ STRIP := strip
 # Specify GMP include and library paths, if not on default search paths.
 WITH_GMP_DIR :=
 ifneq ($(WITH_GMP_DIR),)
-WITH_GMP_INC_DIR := $WITH_GMP_DIR/include
-WITH_GMP_LIB_DIR := $WITH_GMP_DIR/lib
+WITH_GMP_INC_DIR := $(WITH_GMP_DIR)/include
+WITH_GMP_LIB_DIR := $(WITH_GMP_DIR)/lib
 endif
 
 # Specify installation prefix and staged install destination.
diff --git a/Makefile.binary b/Makefile.binary
index 4d6a5fb27c..8baf3e7a3f 100644
--- a/Makefile.binary
+++ b/Makefile.binary
@@ -5,8 +5,8 @@ CC := gcc
 # Specify GMP include and library paths, if not on default search paths.
 WITH_GMP_DIR :=
 ifneq ($(WITH_GMP_DIR),)
-WITH_GMP_INC_DIR := $WITH_GMP_DIR/include
-WITH_GMP_LIB_DIR := $WITH_GMP_DIR/lib
+WITH_GMP_INC_DIR := $(WITH_GMP_DIR)/include
+WITH_GMP_LIB_DIR := $(WITH_GMP_DIR)/lib
 endif
 
 # Specify installation prefix and staged install destination.
diff --git a/runtime/Makefile b/runtime/Makefile
index 1cccbbf8df..f5feeb4eab 100644
--- a/runtime/Makefile
+++ b/runtime/Makefile
@@ -13,8 +13,8 @@ RANLIB := ranlib
 
 WITH_GMP_DIR :=
 ifneq ($(WITH_GMP_DIR),)
-WITH_GMP_INC_DIR := $WITH_GMP_DIR/include
-WITH_GMP_LIB_DIR := $WITH_GMP_DIR/lib
+WITH_GMP_INC_DIR := $(WITH_GMP_DIR)/include
+WITH_GMP_LIB_DIR := $(WITH_GMP_DIR)/lib
 endif
 
 FIND := find