diff --git a/src/asm/actions.cpp b/src/asm/actions.cpp
index f4f7d985..ce3f4f4a 100644
--- a/src/asm/actions.cpp
+++ b/src/asm/actions.cpp
@@ -186,7 +186,10 @@ uint32_t act_CharToNum(std::string const &str) {
 }
 
 uint32_t act_StringToNum(std::string const &str) {
-	warning(WARNING_OBSOLETE, "Treating strings as numbers is deprecated");
+	warning(
+	    WARNING_OBSOLETE,
+	    "Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead"
+	);
 	if (std::vector<int32_t> units = charmap_Convert(str); units.size() == 1) {
 		// The string is a single character with a single unit value,
 		// which can be used directly as a number.
diff --git a/test/asm/empty-strings.err b/test/asm/empty-strings.err
index 00452c02..68158ecd 100644
--- a/test/asm/empty-strings.err
+++ b/test/asm/empty-strings.err
@@ -1,4 +1,4 @@
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at empty-strings.asm(5)
 error: Strings as numbers must be a single charmap unit
     at empty-strings.asm(5)
diff --git a/test/asm/multivalue-charmap.err b/test/asm/multivalue-charmap.err
index 3994c234..3ebddc7c 100644
--- a/test/asm/multivalue-charmap.err
+++ b/test/asm/multivalue-charmap.err
@@ -1,8 +1,8 @@
 warning: All character units must be 8-bit [-Wtruncation]
     at multivalue-charmap.asm(11)
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at multivalue-charmap.asm(20)
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at multivalue-charmap.asm(21)
 warning: All character units must be 8-bit [-Wtruncation]
     at multivalue-charmap.asm(22)
diff --git a/test/asm/nested-bad-interpolation.err b/test/asm/nested-bad-interpolation.err
index 9b7f15cc..97d39375 100644
--- a/test/asm/nested-bad-interpolation.err
+++ b/test/asm/nested-bad-interpolation.err
@@ -6,7 +6,7 @@ error: syntax error, unexpected end of line
     at nested-bad-interpolation.asm(1)
 error: Interpolated symbol `b` is a reserved keyword; add a '#' prefix to use it as a raw symbol
     at nested-bad-interpolation.asm(2)
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at nested-bad-interpolation.asm(2)
 error: Strings as numbers must be a single charmap unit
     at nested-bad-interpolation.asm(2)
@@ -14,7 +14,7 @@ error: Interpolated symbol `c` is a reserved keyword; add a '#' prefix to use it
     at nested-bad-interpolation.asm(3)
 error: Interpolated symbol `` does not exist
     at nested-bad-interpolation.asm(3)
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at nested-bad-interpolation.asm(3)
 error: Strings as numbers must be a single charmap unit
     at nested-bad-interpolation.asm(3)
diff --git a/test/asm/raw-string-symbol-errors.err b/test/asm/raw-string-symbol-errors.err
index ba5783af..3b420521 100644
--- a/test/asm/raw-string-symbol-errors.err
+++ b/test/asm/raw-string-symbol-errors.err
@@ -1,4 +1,4 @@
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at raw-string-symbol-errors.asm(7)
 error: Strings as numbers must be a single charmap unit
     at raw-string-symbol-errors.asm(7)
@@ -10,7 +10,7 @@ error: `m` is not a string symbol
     at raw-string-symbol-errors.asm(13)
 error: `u` is not a string symbol
     at raw-string-symbol-errors.asm(14)
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at raw-string-symbol-errors.asm(17)
 error: Strings as numbers must be a single charmap unit
     at raw-string-symbol-errors.asm(17)
diff --git a/test/asm/string-concat.err b/test/asm/string-concat.err
index beab4e46..ec632d55 100644
--- a/test/asm/string-concat.err
+++ b/test/asm/string-concat.err
@@ -1,6 +1,6 @@
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at string-concat.asm(21)
-warning: Treating strings as numbers is deprecated [-Wobsolete]
+warning: Treating strings as numbers is deprecated; use character literals or `CHARVAL` instead [-Wobsolete]
     at string-concat.asm(21)
 error: syntax error, unexpected ++
     at string-concat.asm(25)