diff --git a/src/template/base/top/configure/CONFIG b/src/template/base/top/configure/CONFIG
index c1a470322..34ace5775 100644
--- a/src/template/base/top/configure/CONFIG
+++ b/src/template/base/top/configure/CONFIG
@@ -8,9 +8,19 @@ RULES = $(EPICS_BASE)
 # RELEASE files point to other application tops
 include $(TOP)/configure/RELEASE
 -include $(TOP)/configure/RELEASE.$(EPICS_HOST_ARCH).Common
+
 ifdef T_A
--include $(TOP)/configure/RELEASE.Common.$(T_A)
--include $(TOP)/configure/RELEASE.$(EPICS_HOST_ARCH).$(T_A)
+  -include $(TOP)/configure/RELEASE.Common.$(T_A)
+  -include $(TOP)/configure/RELEASE.$(EPICS_HOST_ARCH).$(T_A)
+endif
+
+# Check EPICS_BASE is set properly
+ifneq (file,$(origin EPICS_BASE))
+  $(error EPICS_BASE must be set in a configure/RELEASE file)
+else
+  ifeq ($(wildcard $(EPICS_BASE)/configure/CONFIG_BASE),)
+    $(error EPICS_BASE does not point to an EPICS installation)
+  endif
 endif
 
 CONFIG = $(RULES)/configure
@@ -19,11 +29,17 @@ include $(CONFIG)/CONFIG
 # Override the Base definition:
 INSTALL_LOCATION = $(TOP)
 
-# CONFIG_SITE files contain other build configuration settings
+# CONFIG_SITE files contain local build configuration settings
 include $(TOP)/configure/CONFIG_SITE
+
+# Host-arch specific settings
 -include $(TOP)/configure/CONFIG_SITE.$(EPICS_HOST_ARCH).Common
+
 ifdef T_A
+  # Target-arch specific settings
  -include $(TOP)/configure/CONFIG_SITE.Common.$(T_A)
+
+  #  Host & target specific settings
  -include $(TOP)/configure/CONFIG_SITE.$(EPICS_HOST_ARCH).$(T_A)
 endif
 
diff --git a/src/template/ext/top/configure/CONFIG b/src/template/ext/top/configure/CONFIG
index 321f6cea2..0c239bf18 100644
--- a/src/template/ext/top/configure/CONFIG
+++ b/src/template/ext/top/configure/CONFIG
@@ -1,13 +1,11 @@
 # CONFIG - Load build configuration data
 #
-# Do not make changes in this file, any site-specific
-# overrides should be given in a CONFIG_SITE file.
+# Do not make changes to this file!
 
-# Where the build rules come from
+# Allow user to override where the build rules come from
 RULES = $(EPICS_BASE)
 
-INSTALL_IDLFILE = $(INSTALL)
-
+# RELEASE files point to other application tops
 include $(TOP)/configure/RELEASE
 -include $(TOP)/configure/RELEASE.$(EPICS_HOST_ARCH)
 -include $(TOP)/configure/RELEASE.$(EPICS_HOST_ARCH).Common
@@ -17,27 +15,38 @@ ifdef T_A
   -include $(TOP)/configure/RELEASE.$(EPICS_HOST_ARCH).$(T_A)
 endif
 
+# Check EPICS_BASE is set properly
+ifneq (file,$(origin EPICS_BASE))
+  $(error EPICS_BASE must be set in a configure/RELEASE file)
+else
+  ifeq ($(wildcard $(EPICS_BASE)/configure/CONFIG_BASE),)
+    $(error EPICS_BASE does not point to an EPICS installation)
+  endif
+endif
+
 CONFIG = $(RULES)/configure
 include $(CONFIG)/CONFIG
 
-# Override some Base definitions
+# Override the Base definition:
 INSTALL_LOCATION = $(TOP)
 
-# CONFIG_SITE files contain build configuration overrides
+# CONFIG_SITE files contain local build configuration settings
 include $(TOP)/configure/CONFIG_SITE
 
-# Host-arch specific settings
+# Host-arch specific settings for extensions are in configure/os
 -include $(TOP)/configure/os/CONFIG_SITE.$(EPICS_HOST_ARCH).Common
 
+ifdef T_A
+  # Target-arch specific settings for extensions are in configure/os
+  -include $(TOP)/configure/os/CONFIG_SITE.Common.$(T_A)
+
+  #  Host & target specific settings for extensions are in configure/os
+  -include $(TOP)/configure/os/CONFIG_SITE.$(EPICS_HOST_ARCH).$(T_A)
+endif
+
+# Additional settings for extensions
+INSTALL_IDLFILE = $(INSTALL)
+
 ifdef INSTALL_LOCATION_EXTENSIONS
   INSTALL_LOCATION = $(INSTALL_LOCATION_EXTENSIONS)
 endif
-
-ifdef T_A
-  # Target-arch specific settings
-  -include $(TOP)/configure/os/CONFIG_SITE.Common.$(T_A)
-
-  #  Host & target specific combination settings
-  -include $(TOP)/configure/os/CONFIG_SITE.$(EPICS_HOST_ARCH).$(T_A)
-endif
-
diff --git a/src/tools/convertRelease.pl b/src/tools/convertRelease.pl
index 3375eb4f2..b8c596edb 100644
--- a/src/tools/convertRelease.pl
+++ b/src/tools/convertRelease.pl
@@ -227,6 +227,12 @@ sub envPaths {
 # Check RELEASE file consistency with support modules
 #
 sub checkRelease {
+    die "\nEPICS_BASE must be set in a configure/RELEASE file.\n\n"
+        unless grep(m/^(EPICS_BASE)$/, @apps) &&
+            exists $macros{EPICS_BASE} &&
+            $macros{EPICS_BASE} ne '' &&
+            -f "$macros{EPICS_BASE}/configure/CONFIG_BASE";
+
     my $status = 0;
     delete $macros{RULES};
     delete $macros{TOP};