diff --git a/src/input.cpp b/src/input.cpp
index a4cc435953..5e5f1d89c9 100644
--- a/src/input.cpp
+++ b/src/input.cpp
@@ -72,6 +72,7 @@ Input::Input(LAMMPS *lmp, int argc, char **argv) : Pointers(lmp)
   label_active = 0;
   labelstr = NULL;
   jump_skip = 0;
+  ifthenelse_flag = 0;
 
   if (me == 0) {
     nfile = maxfile = 1;
@@ -682,7 +683,9 @@ void Input::ifthenelse()
       ncommands++;
     }
 
+    ifthenelse_flag = 1;
     for (int i = 0; i < ncommands; i++) one(commands[i]);
+    ifthenelse_flag = 0;
 
     for (int i = 0; i < ncommands; i++) delete [] commands[i];
     delete [] commands;
@@ -736,7 +739,9 @@ void Input::ifthenelse()
 
     // execute the list of commands
 
+    ifthenelse_flag = 1;
     for (int i = 0; i < ncommands; i++) one(commands[i]);
+    ifthenelse_flag = 0;
 
     // clean up
 
@@ -753,6 +758,13 @@ void Input::include()
 {
   if (narg != 1) error->all(FLERR,"Illegal include command");
 
+  // do not allow include inside an if command
+  // NOTE: this check will fail if a 2nd if command was inside the if command
+  //       and came before the include
+
+  if (ifthenelse_flag) 
+    error->all(FLERR,"Cannot use include command within an if command");
+
   if (me == 0) {
     if (nfile == maxfile) {
       maxfile++;
diff --git a/src/input.h b/src/input.h
index ca59734e3c..0699cee5d3 100644
--- a/src/input.h
+++ b/src/input.h
@@ -45,6 +45,7 @@ class Input : protected Pointers {
   int label_active;            // 0 = no label, 1 = looking for label
   char *labelstr;              // label string being looked for
   int jump_skip;               // 1 if skipping next jump, 0 otherwise
+  int ifthenelse_flag;         // 1 if executing commands inside an if-then-else
 
   FILE **infiles;              // list of open input files