diff --git a/Makefile b/Makefile
index 28e22324..13ba7e4b 100644
--- a/Makefile
+++ b/Makefile
@@ -75,6 +75,7 @@ libcyclone.a: runtime.c include/cyclone/runtime.h include/cyclone/types.h gc.c d
 	$(CC) $(CFLAGS) -std=gnu99 -c gc.c -o gc.o
 	$(CC) $(CFLAGS) -c \
                   -DCYC_HAVE_OPEN_MEMSTREAM=$(CYC_PLATFORM_HAS_MEMSTREAM) \
+                  -DCYC_HAVE_FMEMOPEN=$(CYC_PLATFORM_HAS_FMEMOPEN) \
                   mstreams.c -o mstreams.o
 	$(CC) $(CFLAGS) -c \
                   -DCYC_INSTALL_DIR=\"$(PREFIX)\" \
diff --git a/Makefile.config b/Makefile.config
index 062e96c4..01e7dbb0 100644
--- a/Makefile.config
+++ b/Makefile.config
@@ -39,6 +39,7 @@ DESTDIR   ?=
 # Automatically detect platform-specific flags, instead of using autoconf
 #CYC_PLATFORM_HAS_MEMSTREAM ?= 1
 CYC_PLATFORM_HAS_MEMSTREAM := $(shell echo "main(){char *buf; int len; open_memstream(&buf, &len);}" | gcc -xc - >/dev/null 2>/dev/null && echo 1 || echo 0)
+CYC_PLATFORM_HAS_FMEMOPEN := $(shell echo "main(){char *buf; fmemopen(&buf, 0, \"r\");}" | gcc -xc - >/dev/null 2>/dev/null && echo 1 || echo 0)
 
 # code from chibi's makefile to detect platform
 ifndef PLATFORM
diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index ce05dc43..87d9469f 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -217,6 +217,7 @@ port_type Cyc_stderr(void);
 port_type Cyc_io_open_input_file(void *data, object str);
 port_type Cyc_io_open_output_file(void *data, object str);
 port_type *Cyc_io_open_output_string(void *data);
+port_type *Cyc_io_open_input_string(void *data, object str);
 void Cyc_io_get_output_string(void *data, object cont, object port);
 object Cyc_io_close_port(void *data, object port);
 object Cyc_io_close_input_port(void *data, object port);
diff --git a/mstreams.c b/mstreams.c
index 323fc620..9cac2044 100644
--- a/mstreams.c
+++ b/mstreams.c
@@ -11,8 +11,6 @@
 #include "cyclone/types.h"
 #include "cyclone/runtime.h"
 #include <errno.h>
-//#include <limits.h>
-//#include <ctype.h>
 
 /* These macros are hardcoded here to support functions in this module. */
 #define closcall1(td, clo, a1) \
@@ -34,6 +32,27 @@ if (type_is_pair_prim(clo)) { \
 }
 
 object Cyc_heap_alloc_port(void *data, port_type *p);
+port_type *Cyc_io_open_input_string(void *data, object str)
+{
+//  // Allocate port on the heap so the location of mem_buf does not change
+  port_type *p;
+  make_port(sp, NULL, 0);
+
+  Cyc_check_str(data, str);
+  p = (port_type *)Cyc_heap_alloc_port(data, &sp);
+  errno = 0;
+#if CYC_HAVE_FMEMOPEN
+  p->mem_buf = malloc(sizeof(char) * (string_len(str) + 1));
+  p->mem_buf_len = string_len(str);
+  memcpy(p->mem_buf, string_str(str), string_len(str));
+  p->fp = fmemopen(p->mem_buf, string_len(str) + 1, "r");
+#endif
+  if (p->fp == NULL){
+    Cyc_rt_raise2(data, "Unable to open input memory stream", obj_int2obj(errno));
+  }
+  return p;
+}
+
 port_type *Cyc_io_open_output_string(void *data)
 {
   // Allocate port on the heap so the location of mem_buf does not change
@@ -45,7 +64,7 @@ port_type *Cyc_io_open_output_string(void *data)
   p->fp = open_memstream(&(p->mem_buf), &(p->mem_buf_len));
 #endif
   if (p->fp == NULL){
-    Cyc_rt_raise2(data, "Unable to open memory stream", obj_int2obj(errno));
+    Cyc_rt_raise2(data, "Unable to open output memory stream", obj_int2obj(errno));
   }
   return p;
 }
diff --git a/scheme/base.sld b/scheme/base.sld
index 2b5221a3..65467137 100644
--- a/scheme/base.sld
+++ b/scheme/base.sld
@@ -140,6 +140,7 @@
     output-port-open?
     get-output-string
     open-output-string
+    open-input-string
     features
     Cyc-version
     any
@@ -194,11 +195,6 @@
 ;    ; No complex or rational numbers at this time
 ;    rationalize
 ;
-;    ; need string ports
-;    ; may be able to use POSIX string steams for this, see: open_memstream
-;    ; however there may be portability issues with that. looks like BSD and windows don't have it
-;    open-input-string
-;
 ;    ;; no binary/text ports yet
 ;    binary-port?
 ;    textual-port?
@@ -1161,6 +1157,10 @@
         data, 
         k, 
        ((p->mode == 0 && p->fp != NULL) ? boolean_t : boolean_f)); ")
+  (define-c open-input-string
+    "(void *data, int argc, closure _, object k, object str)"
+    " port_type *p = Cyc_io_open_input_string(data, str);
+      return_closcall1(data, k, p); ")
   (define-c open-output-string
     "(void *data, int argc, closure _, object k)"
     " port_type *p = Cyc_io_open_output_string(data);