diff --git a/src/MPIIO/dump_custom_mpiio.cpp b/src/MPIIO/dump_custom_mpiio.cpp
index f07c1e19d6..678ee3dadd 100644
--- a/src/MPIIO/dump_custom_mpiio.cpp
+++ b/src/MPIIO/dump_custom_mpiio.cpp
@@ -231,10 +231,12 @@ void DumpCustomMPIIO::init_style()
   // lo priority = line, medium priority = int/float, hi priority = column
 
   auto words = utils::split_words(format);
-  if ((int) words.size() < nfield) error->all(FLERR, "Dump_modify format line is too short");
+  if ((int) words.size() < nfield)
+    error->all(FLERR, "Dump_modify format line is too short: {}", format);
 
   int i = 0;
   for (const auto &word : words) {
+    if (i >= nfield) break;
     delete[] vformat[i];
 
     if (format_column_user[i])
diff --git a/src/dump_custom.cpp b/src/dump_custom.cpp
index 9389839aca..cd85671578 100644
--- a/src/dump_custom.cpp
+++ b/src/dump_custom.cpp
@@ -262,10 +262,11 @@ void DumpCustom::init_style()
 
   auto words = utils::split_words(format);
   if ((int) words.size() < nfield)
-    error->all(FLERR,"Dump_modify format line is too short");
+    error->all(FLERR,"Dump_modify format line is too short: {}", format);
 
   int i=0;
   for (const auto &word : words) {
+    if (i >= nfield) break;
     delete[] vformat[i];
 
     if (format_column_user[i])
diff --git a/src/dump_local.cpp b/src/dump_local.cpp
index 5fad243e74..bf26890b05 100644
--- a/src/dump_local.cpp
+++ b/src/dump_local.cpp
@@ -185,10 +185,11 @@ void DumpLocal::init_style()
 
   auto words = utils::split_words(format);
   if ((int) words.size() <  size_one)
-    error->all(FLERR,"Dump_modify format line is too short");
+    error->all(FLERR,"Dump_modify format line is too short: {}", format);
 
   int i=0;
   for (const auto &word : words) {
+    if (i >= size_one) break;
     delete[] vformat[i];
 
     if (format_column_user[i])