diff --git a/src/AMOEBA/amoeba_convolution.cpp b/src/AMOEBA/amoeba_convolution.cpp
index 68da7ca7e5..f222613c3c 100644
--- a/src/AMOEBA/amoeba_convolution.cpp
+++ b/src/AMOEBA/amoeba_convolution.cpp
@@ -615,9 +615,7 @@ void AmoebaConvolution::debug_file(int array, const char *label)
 
   // open file
 
-  char fname[128];
-  sprintf(fname,"tmp.%s.%s",labels[which],label);
-  if (me == 0) fp = fopen(fname,"w");
+  if (me == 0) fp = fopen(fmt::format("tmp.{}.{}", labels[which], label).c_str(), "w");
 
   // file header
   // ncol = # of columns, including grid cell ID
diff --git a/src/variable.cpp b/src/variable.cpp
index 65a1f7d885..e5b192c607 100644
--- a/src/variable.cpp
+++ b/src/variable.cpp
@@ -959,7 +959,8 @@ char *Variable::retrieve(const char *name)
     str = data[ivar][0] = utils::strdup(result);
   } else if (style[ivar] == EQUAL) {
     double answer = evaluate(data[ivar][0],nullptr,ivar);
-    sprintf(data[ivar][1],"%.15g",answer);
+    delete[] data[ivar][1];
+    data[ivar][1] = utils::strdup(fmt::format("{:.15g}",answer));
     str = data[ivar][1];
   } else if (style[ivar] == FORMAT) {
     int jvar = find(data[ivar][0]);
@@ -1000,7 +1001,8 @@ char *Variable::retrieve(const char *name)
     char *strlong = python->long_string(ifunc);
     if (strlong) str = strlong;
   } else if (style[ivar] == TIMER || style[ivar] == INTERNAL) {
-    sprintf(data[ivar][0],"%.15g",dvalue[ivar]);
+    delete[] data[ivar][0];
+    data[ivar][0] = utils::strdup(fmt::format("{:.15g}",dvalue[ivar]));
     str = data[ivar][0];
   } else if (style[ivar] == ATOM || style[ivar] == ATOMFILE ||
              style[ivar] == VECTOR) return nullptr;