diff --git a/src/racket/gc/Makefile.in b/src/racket/gc/Makefile.in
index 1d4d29b2c5..7422e6540b 100644
--- a/src/racket/gc/Makefile.in
+++ b/src/racket/gc/Makefile.in
@@ -19,6 +19,11 @@ AS_ABI_FLAG=$(ABI_FLAG)
 # ABI flag for assembler.  On HP/UX this is +A64 for 64 bit
 # executables.
 
+# PLTSCHEME: these paths are ultimately used for installing libs:
+prefix = @prefix@
+exec_prefix = @exec_prefix@
+libdir = @libdir@
+
 CC= @CC@ $(ABI_FLAG)
 CXX= @CXX@ $(ABI_FLAG)
 AS= @AS@ $(ABI_FLAG)
diff --git a/src/racket/sgc/Makefile.in b/src/racket/sgc/Makefile.in
index 6598e6784f..98e74000fd 100644
--- a/src/racket/sgc/Makefile.in
+++ b/src/racket/sgc/Makefile.in
@@ -3,6 +3,9 @@
 #
 
 srcdir = @srcdir@
+prefix = @prefix@
+exec_prefix = @exec_prefix@
+libdir = @libdir@
 
 CC = @CC@
 CXX = @CXX@