diff --git a/src/spicelib/devices/isrc/isrc.c b/src/spicelib/devices/isrc/isrc.c
index d6801e8ef..8272357f8 100644
--- a/src/spicelib/devices/isrc/isrc.c
+++ b/src/spicelib/devices/isrc/isrc.c
@@ -26,7 +26,7 @@ IFparm ISRCpTable[] = { /* parameters */
  IOP ("trnoise", ISRC_TRNOISE,   IF_REALVEC,"Transient noise description"),
  IOP ("trrandom", ISRC_TRRANDOM, IF_REALVEC,"random source description"),
 #ifdef SHARED_MODULE
- IOP ("external", ISRC_EXTERNAL, IF_REALVEC,"external source description"),
+ IOP ("external", ISRC_EXTERNAL, IF_STRING,"external source description"),
 #endif
  OPU ("pos_node",ISRC_POS_NODE,  IF_INTEGER,"Positive node of source"),
  OPU ("neg_node",ISRC_NEG_NODE,  IF_INTEGER,"Negative node of source"),