diff --git a/src/log/slog/record.go b/src/log/slog/record.go
index d77a6eddca..77dcc477fd 100644
--- a/src/log/slog/record.go
+++ b/src/log/slog/record.go
@@ -166,11 +166,11 @@ type Source struct {
 	// Function is the package path-qualified function name containing the
 	// source line. If non-empty, this string uniquely identifies a single
 	// function in the program. This may be the empty string if not known.
-	Function string
+	Function string `json:"function"`
 	// File and Line are the file name and line number (1-based) of the source
 	// line. These may be the empty string and zero, respectively, if not known.
-	File string
-	Line int
+	File string `json:"file"`
+	Line int    `json:"line"`
 }
 
 // attrs returns the non-zero fields of s as a slice of attrs.