diff --git a/Sources/removemacai/SelfTest.swift b/Sources/removemacai/SelfTest.swift
index 029eb06..6873e4e 100644
--- a/Sources/removemacai/SelfTest.swift
+++ b/Sources/removemacai/SelfTest.swift
@@ -267,6 +267,9 @@ func selfTest() -> Bool {
     "CLICOLOR_FORCE turns color on and off regardless of the terminal")
   check(Term.paint("x", "31", useColor: true).contains("\u{1B}[31m") && !Term.paint("x", "31", useColor: false).contains("\u{1B}"),
     "stderr text is only colored when its own stream allows it")
+  check(Term.size(999_999_999) == "1.0 GB" && Term.size(999_500_000) == "1.0 GB"
+    && Term.size(999_499_999) == "999 MB" && Term.size(1_000_000_000) == "1.0 GB"
+    && Term.size(5_000_000) == "5 MB", "sizes that round to 1000 MB are shown in GB")
   check(Storage.isAppleCache("/x/com.apple.Safari") && Storage.isAppleCache("/x/CloudKit")
     && Storage.isAppleCache("/x/GeoServices") && !Storage.isAppleCache("/x/Homebrew")
     && !Storage.isAppleCache("/x/com.google.Chrome"), "macOS caches without the com.apple. prefix are left alone")
diff --git a/Sources/removemacai/Term.swift b/Sources/removemacai/Term.swift
index 17793a3..5469579 100644
--- a/Sources/removemacai/Term.swift
+++ b/Sources/removemacai/Term.swift
@@ -21,7 +21,8 @@ enum Term {
 
   static func size(_ bytes: Int64) -> String {
     if bytes <= 0 { return "0 MB" }
-    if bytes >= 1_000_000_000 { return String(format: "%.1f GB", Double(bytes) / 1e9) }
+    // Anything that would round to "1000 MB" is shown in GB instead.
+    if bytes >= 999_500_000 { return String(format: "%.1f GB", Double(bytes) / 1e9) }
     return String(format: "%.0f MB", max(1, Double(bytes) / 1e6))
   }