diff --git a/CMakeLists.txt b/CMakeLists.txt
index 430b26d..cb7d6fa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,8 +65,8 @@ if(UTF8PROC_ENABLE_TESTING)
   enable_testing()
   file(MAKE_DIRECTORY data)
   set(UNICODE_VERSION 13.0.0)
-  file(DOWNLOAD http://www.unicode.org/Public/${UNICODE_VERSION}/ucd/NormalizationTest.txt data/NormalizationTest.txt SHOW_PROGRESS)
-  file(DOWNLOAD http://www.unicode.org/Public/${UNICODE_VERSION}/ucd/auxiliary/GraphemeBreakTest.txt data/GraphemeBreakTest.txt SHOW_PROGRESS)
+  file(DOWNLOAD https://www.unicode.org/Public/${UNICODE_VERSION}/ucd/NormalizationTest.txt data/NormalizationTest.txt SHOW_PROGRESS)
+  file(DOWNLOAD https://www.unicode.org/Public/${UNICODE_VERSION}/ucd/auxiliary/GraphemeBreakTest.txt data/GraphemeBreakTest.txt SHOW_PROGRESS)
   add_executable(case test/tests.h test/tests.c utf8proc.h test/case.c)
   target_link_libraries(case utf8proc)
   add_executable(custom test/tests.h test/tests.c utf8proc.h test/custom.c)
diff --git a/data/Makefile b/data/Makefile
index 26b612d..3793bfa 100644
--- a/data/Makefile
+++ b/data/Makefile
@@ -25,31 +25,31 @@ CharWidths.txt: charwidths.jl EastAsianWidth.txt
 UNICODE_VERSION=13.0.0
 
 UnicodeData.txt:
-	$(CURL) $(CURLFLAGS) -o $@ http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/UnicodeData.txt
+	$(CURL) $(CURLFLAGS) -o $@ https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/UnicodeData.txt
 
 EastAsianWidth.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/EastAsianWidth.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/EastAsianWidth.txt
 
 GraphemeBreakProperty.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/auxiliary/GraphemeBreakProperty.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/auxiliary/GraphemeBreakProperty.txt
 
 DerivedCoreProperties.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/DerivedCoreProperties.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/DerivedCoreProperties.txt
 
 CompositionExclusions.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/CompositionExclusions.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/CompositionExclusions.txt
 
 CaseFolding.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/CaseFolding.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/CaseFolding.txt
 
 NormalizationTest.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/NormalizationTest.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/NormalizationTest.txt
 
 GraphemeBreakTest.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/auxiliary/GraphemeBreakTest.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://www.unicode.org/Public/$(UNICODE_VERSION)/ucd/auxiliary/GraphemeBreakTest.txt
 
 emoji-data.txt:
-	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)http://unicode.org/Public/$(UNICODE_VERSION)/ucd/emoji/emoji-data.txt
+	$(CURL) $(CURLFLAGS) -o $@ $(URLCACHE)https://unicode.org/Public/$(UNICODE_VERSION)/ucd/emoji/emoji-data.txt
 
 clean:
 	rm -f UnicodeData.txt EastAsianWidth.txt GraphemeBreakProperty.txt DerivedCoreProperties.txt CompositionExclusions.txt CaseFolding.txt NormalizationTest.txt GraphemeBreakTest.txt CharWidths.txt emoji-data.txt
diff --git a/utf8proc.c b/utf8proc.c
index cdf8e88..23ff0fb 100644
--- a/utf8proc.c
+++ b/utf8proc.c
@@ -27,7 +27,7 @@
  *  Unicode data files.
  *
  *  The original data files are available at
- *  http://www.unicode.org/Public/UNIDATA/
+ *  https://www.unicode.org/Public/UNIDATA/
  *
  *  Please notice the copyright statement in the file "utf8proc_data.c".
  */