diff --git a/prism/src/parser/PrismParser.java b/prism/src/parser/PrismParser.java
index 57a4d4b8..a1decf88 100644
--- a/prism/src/parser/PrismParser.java
+++ b/prism/src/parser/PrismParser.java
@@ -1279,7 +1279,7 @@ public class PrismParser implements PrismParserConstants {
       sys2 = SystemParallel();
                                                                                                                                par.addOperand(sys2);
     }
-                if (par==null) {
+                if (par==null || par.getNumOperands() == 1) {
                         {if (true) return sys1;}
                 }
                 else {
@@ -1310,7 +1310,7 @@ public class PrismParser implements PrismParserConstants {
       sys2 = SystemFullParallel();
                                                                                                                                              par.addOperand(sys2);
     }
-                if (par==null) {
+                if (par==null || par.getNumOperands() == 1) {
                         {if (true) return sys1;}
                 }
                 else {
diff --git a/prism/src/parser/PrismParser.jj b/prism/src/parser/PrismParser.jj
index d7b9e175..615d02c8 100644
--- a/prism/src/parser/PrismParser.jj
+++ b/prism/src/parser/PrismParser.jj
@@ -911,7 +911,7 @@ SystemDefn SystemFullParallel() :
 	sys1 = SystemInterleaved()
 	( { par = new SystemFullParallel(); par.addOperand(sys1); } ( LOOKAHEAD(<OR> <OR>) <OR> <OR> sys2 = SystemParallel() { par.addOperand(sys2); } )* )
 	{
-		if (par==null) {
+		if (par==null || par.getNumOperands() == 1) {
 			return sys1;
 		}
 		else {
@@ -934,7 +934,7 @@ SystemDefn SystemInterleaved() :
 	sys1 = SystemParallel()
 	( { par = new SystemInterleaved(); par.addOperand(sys1); } ( LOOKAHEAD(<OR> <OR> <OR>) <OR> <OR> <OR>  sys2 = SystemFullParallel() { par.addOperand(sys2); } )* )
 	{
-		if (par==null) {
+		if (par==null || par.getNumOperands() == 1) {
 			return sys1;
 		}
 		else {