diff --git a/src/factory/FieldCreateFactory.cpp b/src/factory/FieldCreateFactory.cpp
index 6c5f9b0d..561e8ee4 100644
--- a/src/factory/FieldCreateFactory.cpp
+++ b/src/factory/FieldCreateFactory.cpp
@@ -15,6 +15,7 @@
 #include <sstream>
 
 #include <epicsString.h>
+#include <epicsStdio.h>
 #include <epicsMutex.h>
 #include <epicsThread.h>
 
@@ -378,7 +379,8 @@ BoundedScalarArray::BoundedScalarArray(ScalarType elementType, size_t size)
 string BoundedScalarArray::getID() const
 {
     char buffer[32];
-    sprintf(buffer, "%s<%zu>", ScalarTypeFunc::name(getElementType()), size);
+    epicsSnprintf(buffer, sizeof(buffer), "%s<%lu>",
+        ScalarTypeFunc::name(getElementType()), (unsigned long) size);
     return string(buffer);
 }
 
@@ -403,7 +405,8 @@ FixedScalarArray::FixedScalarArray(ScalarType elementType, size_t size)
 string FixedScalarArray::getID() const
 {
     char buffer[32];
-    sprintf(buffer, "%s[%zu]", ScalarTypeFunc::name(getElementType()), size);
+    epicsSnprintf(buffer, sizeof(buffer), "%s[%lu]",
+        ScalarTypeFunc::name(getElementType()), (unsigned long) size);
     return string(buffer);
 }
 
diff --git a/testApp/pv/performstruct.cpp b/testApp/pv/performstruct.cpp
index 7abf1a8b..0b78ac03 100644
--- a/testApp/pv/performstruct.cpp
+++ b/testApp/pv/performstruct.cpp
@@ -6,6 +6,7 @@
 
 #include <testMain.h>
 #include <epicsUnitTest.h>
+#include <epicsStdio.h>
 
 #include <pv/current_function.h>
 #include <pv/pvData.h>
@@ -54,7 +55,7 @@ void buildMiss()
     for(size_t i=0; i<1000; i++) {
         // unique name each time to (partially) defeat caching
         char buf[10];
-        sprintf(buf, "field%zu", i);
+        epicsSnprintf(buf, sizeof(buf), "field%lu", (unsigned long) i);
 
         record.start();