diff --git a/base/ryu/exp.jl b/base/ryu/exp.jl
index cf1fe23105b8c..6356206971f8b 100644
--- a/base/ryu/exp.jl
+++ b/base/ryu/exp.jl
@@ -213,7 +213,7 @@
         roundPos = pos
         while true
             roundPos -= 1
-            if roundPos == (startpos - 1) || buf[roundPos] == UInt8('-')
+            if roundPos == (startpos - 1) || buf[roundPos] == UInt8('-') || (plus && buf[roundPos] == UInt8('+')) || (space && buf[roundPos] == UInt8(' '))
                 buf[roundPos + 1] = UInt8('1')
                 e += 1
                 break
diff --git a/base/ryu/fixed.jl b/base/ryu/fixed.jl
index 4be1b3741832e..14713111a95a1 100644
--- a/base/ryu/fixed.jl
+++ b/base/ryu/fixed.jl
@@ -166,7 +166,7 @@
             dotPos = 1
             while true
                 roundPos -= 1
-                if roundPos == (startpos - 1) || (buf[roundPos] == UInt8('-'))
+                if roundPos == (startpos - 1) || (buf[roundPos] == UInt8('-')) || (plus && buf[roundPos] == UInt8('+')) || (space && buf[roundPos] == UInt8(' '))
                     buf[roundPos + 1] = UInt8('1')
                     if dotPos > 1
                         buf[dotPos] = UInt8('0')
diff --git a/stdlib/Printf/test/runtests.jl b/stdlib/Printf/test/runtests.jl
index d38c90734d4f1..c74739d66ba51 100644
--- a/stdlib/Printf/test/runtests.jl
+++ b/stdlib/Printf/test/runtests.jl
@@ -141,6 +141,10 @@ end
     @test Printf.@sprintf("%+ 09.1f", 1.234) == "+000001.2"
     @test Printf.@sprintf("%+ 09.0f", 1.234) == "+00000001"
     @test Printf.@sprintf("%+ #09.0f", 1.234) == "+0000001."
+
+    #40303
+    @test Printf.@sprintf("%+7.1f", 9.96) == "  +10.0"
+    @test Printf.@sprintf("% 7.1f", 9.96) == "   10.0"
 end
 
 @testset "%e" begin
@@ -202,6 +206,10 @@ end
     @test Printf.@sprintf("%+ 09.1e", 1.234) == "+01.2e+00"
     @test Printf.@sprintf("%+ 09.0e", 1.234) == "+0001e+00"
     @test Printf.@sprintf("%+ #09.0e", 1.234) == "+001.e+00"
+
+    #40303
+    @test Printf.@sprintf("%+9.1e", 9.96) == " +1.0e+01"
+    @test Printf.@sprintf("% 9.1e", 9.96) == "  1.0e+01"
 end
 
 @testset "strings" begin